Fuel pump failures

I know this is a much discussed issue, but I wanted to bring it up again as it is a constant headache for many, me included.
I am looking for insight, solutions, etc...
History:
I have an 81 that I have owned for a year now. I have done a good bit o work on the car to included the fuel system. New Fuel distro, steel braided fuel lines, new fuel pump, accumulator, and J Herveys fuel pump kit with his fuel pump. The Car had fuel pump issues before I owned it(records) and it had a J Hervey(JH) pump in it then. It also had the stock fuel pump kit in the tank. The tank is spotless, no contamination.
The car took a dump on me a few times and quickly figured the pump as the culprit. It would get hot(summer time in ABQ NM) and the pump would get louder and louder. Finally the car would start to buck and sputter till it would just die. So, I ( novice D owner) talked with JH and he said his kit was great so I bought it.
The car failed shortly thereafter(last summer). New Fuel pump( from JH) and cooler temps brought a a good driving car that is driven a few times a week.
I recently overhauled the entire cooling system. New, electric, fans for the radiator. water pump, silicon lines, etc..
Anyway, two weeks ago(high 80s) I was driving with 1/4 tank of gas and the F pump start to scream. I quickly found a gas station topped off and the sound was gone, back to normal. Last week, while driving in city traffic(90deg F, mid day) the car got just above 220deg and then the pump started to sputter again(3/4 tank of gas). I drove it another 7 miles before the car died. I had to let her cool off a few hours and she started right up.

Questions:
I am certain the issue is the fuel pump, but why? It is a JH pump and it worked well thru the winter, but AS SOON as it got hot again, she crapped out.
Both cooling fans are working well. Are they heating up the fuel tank? Does deflecting the air from the tank help? I want to fix this and hope y'all can help!
LASTLY, of those that have seen or own the new DMC pump/sender unit, what are your thoughts?
Is there a good fuel pump out there? How/where do you get it?
Thanks

There are many possible sources of a problem, but I'd start with the easiest to check: electrical. I would backprobe the fuel pump's connector to make sure you have good connectivity. Weak voltage or bad ground would make the pump overheat.

Try putting a spring into the pick-up hose and make sure when the pump is installed you do not twist and kink the hose. The problem is not the pump. The problem is your pick-up hose is collapsing or kinking and starving the fuel pump. That's why it gets louder and the motor stops. Keeping more than 1/2 tank of fuel helps to prevent this but the fix is to put a spring inside that hose.
David Teitelbaum

kinda sounds like vapor lock problems, im only really familiar with vapor lock bc of of my old Volvo 240 (with K-jet) had it when i was younger, so im not an expert on it... but the idea is that as it gets weather gets hotter the fuel is turning to vapor in the fuel lines and messes with the pressure on the way to the engine. Thus starving the engine of fuel. On our Volvo we replaced the intank and inline fuel pump, and it solved problem. The fuel pump should keep the pressure constant forcing into the fuel in there.

I dont know too much about those fuel pumps from Hervey, but i did hear really good things abut DMC's kit, and came HIGHLY recommended from my mechanic in boulder.

I know that Tom Quirk Automotive on Girard, near Candelaria, has worked on DeLorean's in the past. and probably could point you in the right direction.

Did you have John's "power pump"? He claimed that one to never make noise.

The fuel in the tank does get very hot. I did some testing with a sensor in the tank and I seem to remember when it got above 125 deg F the pump would make noise.

So far I have not heard any noise complaints from the new DMCH fuel pump/sender unit. I still run a stock pump but I installed a cooler on the fuel return line. If I had not done that, I would try that new DMCH pump.

I have to new combo unit... the install is very easy, it is a new modified GM pump, Very quiet, has a self contained fuel pick-up, and I have had no heat issues. Well worth the money to me.

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Originally Posted by Silverbullet

I have to new combo unit... the install is very easy, it is a new modified GM pump, Very quiet, has a self contained fuel pick-up, and I have had no heat issues. Well worth the money to me.

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...gotta love the built-in level sending unit.... Way to go if you aren't worried about originality, so to answer your other question, I'd call DMCMW -- they will fix you up, fast, and give great support.

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Originally Posted by Bitsyncmaster

I still run a stock pump but I installed a cooler on the fuel return line.

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where do you have installed the fuel cooler?

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Originally Posted by BABIS

where do you have installed the fuel cooler?

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http://dmctalk.org/showthread.php?15...p-buzzing-cure

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Originally Posted by Ron

http://dmctalk.org/showthread.php?15...p-buzzing-cure

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Thanks!

Your current pump is on its way out. There are many things mentioned above that can cause a noisy pump, but it can very well be the pump itself. My old pump did the same thing...for over a year! whenever it got hot it hummed and if I kept driving, it would eventually stop altogether. I tried all the fixes, spring in the pickup hose, fresh gas when it made noise, making sure the pickup was not twisting due to improper pump reassembled, etc. Once during a fairly warm day while going over a mountain, she started groaning and finally crapped out. After it cooled down a bit it performed perfectly. I have previously dismissed the pump being the culprit since it always worked fine shortly after and I had been going on advice about this common problem being related to other things. 2 years ago, I finally realized this could be the pump itself and replaced with a DMC pump, (not hervey's junk) and its been fine ever since. I have even driven this car in 107 degree weather in stop and go traffic with no humming or noise.

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Originally Posted by Ron

...gotta love the built-in level sending unit.... Way to go if you aren't worried about originality...

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Do concours judges open up the fuel system to check?

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Originally Posted by Michael

Do concours judges open up the fuel system to check?

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LMAO -- Good question!

You really don't think anyone would cheat, do you?

The short answer is no. For a more comprehensive answer refer to the Millenium Concours Manual. Originality can only go so far. Do you have original gas, air in the tires, tires, battery, struts, etc? Of course not.
David Teitelbaum

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Originally Posted by David T

The short answer is no. For a more comprehensive answer refer to the Millenium Concours Manual. Originality can only go so far. Do you have original gas, air in the tires, tires, battery, struts, etc? Of course not.
David Teitelbaum

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Let me extinguish this before it gets out of hand...I was joking. :elmo3:

Thanks for the insight. Out of general curiosity, I think I will buy one of the DMC pumps and check out all connections. see how that fares. If it fails, I will pick up the new DMC unit. Fingers crossed:)

I've heard that some owners have a plate of something that forces air up to the fuel tank. Does anyone have this? Pictures? I guess the theories are that fuel is heated by air from the radiator fans, or hot fuel return. The first seems like the easier fix.
???

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Originally Posted by dvfr750f

I've heard that some owners have a plate of something that forces air up to the fuel tank. Does anyone have this? Pictures? I guess the theories are that fuel is heated by air from the radiator fans, or hot fuel return. The first seems like the easier fix.
???

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You may be referring to the "hot air dam."

Attachment 19507

The picture is of John Hervey's, from his website.

Quote:

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Originally Posted by dvfr750f

I've heard that some owners have a plate of something that forces air up to the fuel tank. Does anyone have this? Pictures? I guess the theories are that fuel is heated by air from the radiator fans, or hot fuel return. The first seems like the easier fix.
???

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Yes I have the hot air dam. My feeling is it does nothing to cool the fuel in the tank. I do not have test data to prove or disprove that though.

What about directing air up to it? I spoke with one of the guys at DMC CA and he seemed to think that you can direct fresh air up to the fuel tank to provide a cooling effect. THoughts?

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Originally Posted by dvfr750f

What about directing air up to it? I spoke with one of the guys at DMC CA and he seemed to think that you can direct fresh air up to the fuel tank to provide a cooling effect. THoughts?

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??? Your choice of the words "seemed to think" implies that you either talked to someone who didn't know what they were talking about, or you've paraphrased it incorrectly.

That is really not possible. Half of the air entering the area is already heated by the radiator/condenser no matter what you do, and the other 50% is just there. The tank is surrounded by the frame. Not many parts are actually exposed to the free airflow, so any "cooling" would need to fight the already heated air from the radiator (concept of the "hot air damn"), then it would need to cool down the frame contacting the tank, then the tank itself which is made of plastic (already a decent insulator). The only real way of cooling the tank via convection would be the *very* small amount of heat transferred from the bottom of the tank through the closing plate, then to the free air stream below the car when traveling at a high velocity. And that already happens to every car.

What you need is a heat sink inside the tank and continuing outside the tank. But I still would not want that heat sink sticking below closing plate.

The problem persists! I need help stat !
So I have installed a new DMC fuel pump and after driving for about 20 90deg heat in city traffic. Water temps are well below 220f. The fuel in the tank is cool (I checked). The pump starts screaming so I have pulled over to let things cool down. I have replaced every component in the system over the past year. She runs fine in cold weather.
No one seems to know what's up. I'm hoping someone can help.

Forgive me if you've mentioned this before, but have you confirmed good voltage and good ground at the pump itself?

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Originally Posted by dvfr750f

The problem persists! I need help stat !
So I have installed a new DMC fuel pump and after driving for about 20 90deg heat in city traffic. Water temps are well below 220f. The fuel in the tank is cool (I checked). The pump starts screaming so I have pulled over to let things cool down. I have replaced every component in the system over the past year. She runs fine in cold weather.
No one seems to know what's up. I'm hoping someone can help.

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How did you check the tank temp? I bet if you stuck you hand into the open tank you would feel really hot fuel. Do you have the new DMC pump and sender or just a new old style pump?

Could it be the fuel pickup line getting kinked?

A couple things that it would be good to know:

1. Is this pump getting 12V with a solid and dedicated ground?

2. You mentioned you had John's pump in the car - which one? His $89 one? His power pump? Bosch 957 pump? What pump specifically of his was in the car?

3. I read that you had the stock fuel baffle kit in the car - when you bought John's pump, did you ever get his fuel baffle kit? Picture below is what I am referring to:

Attachment 19966

Quote:

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Originally Posted by dvfr750f

The problem persists! I need help stat !
So I have installed a new DMC fuel pump and after driving for about 20 90deg heat in city traffic. Water temps are well below 220f. The fuel in the tank is cool (I checked). The pump starts screaming so I have pulled over to let things cool down. I have replaced every component in the system over the past year. She runs fine in cold weather.
No one seems to know what's up. I'm hoping someone can help.

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Ah... When you said the new DMC pump...you are not talking about the new combo unit, right? I have it, and it is GREAT...

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Originally Posted by Silverbullet

Ah... When you said the new DMC pump...you are not talking about the new combo unit, right? I have it, and it is GREAT...

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Agreed. Definitely worth the money - nice quiet pump, and the pump is always submerged with fresh fuel from the return line.

So I have John herveys pump kit with the 'tuna can'. I tend to go thru pumps in the summer so heat is the culprit, but how?
Here is what I think.

I am getting 12.46 v at the pump when under load. The RPM relay is functioning and looks clean, but does have a slightly burnt odor to it. It does get quite hot while driving. Anyone know what the normal op temp is for this?
I bought a new pump from DMC(looks identical to Herveys pump). I installed it and after about 30 min in city traffic on a 90 deg day it began to cavitate.
I pulled over checked the fuel by removing the send unit and just sticking a finger in. The fuel didnt feel very hot. The water temp was mid way from btm to the 220 mark. I then placed a bag of ice right ontop of the fuel lines and the pump(top), let her sit for an hour then drove home. I managed to make it the 10 miles home. The pump screamed the whole way.
SOOOO, I believe it is a heat problem but not an electrical one.
I recently overhauled the entire cooling system to include a new radiator and elec fans. Before this, one of the original fans was not functioning so now the car is pulling ALOT more heat from the radiator and sending that heated air right over the tank and superheating the fuel lines and the top of the pump. I also am getting a fuel odor in the cabin. I suspect that this is the problem.
Today I fabricated an air dam out of thin sheet metal and this has removed ALL air from the radiator to being pushed over the tank. I also put a foam insulation over the two fuel lines. I will drive tomorrow and see how she performs.

you should use the same product used in the exhaust headers as
cover the cooling tubes in the fuel tank area
controlling the transfer of heat between the cooling tubes and the gas tank
so the fuel pump is not affected by heat and the engine will have better performance
Heat is the horsepower and performance killer.


http://www.thermotec.com/products/11...ader-wrap.html

Quote:

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Originally Posted by dvfr750f

So I have John herveys pump kit with the 'tuna can'. I tend to go thru pumps in the summer so heat is the culprit, but how?
Here is what I think.

I am getting 12.46 v at the pump when under load. The RPM relay is functioning and looks clean, but does have a slightly burnt odor to it. It does get quite hot while driving. Anyone know what the normal op temp is for this?
I bought a new pump from DMC(looks identical to Herveys pump). I installed it and after about 30 min in city traffic on a 90 deg day it began to cavitate.
I pulled over checked the fuel by removing the send unit and just sticking a finger in. The fuel didnt feel very hot. The water temp was mid way from btm to the 220 mark. I then placed a bag of ice right ontop of the fuel lines and the pump(top), let her sit for an hour then drove home. I managed to make it the 10 miles home. The pump screamed the whole way.
SOOOO, I believe it is a heat problem but not an electrical one.
I recently overhauled the entire cooling system to include a new radiator and elec fans. Before this, one of the original fans was not functioning so now the car is pulling ALOT more heat from the radiator and sending that heated air right over the tank and superheating the fuel lines and the top of the pump. I also am getting a fuel odor in the cabin. I suspect that this is the problem.
Today I fabricated an air dam out of thin sheet metal and this has removed ALL air from the radiator to being pushed over the tank. I also put a foam insulation over the two fuel lines. I will drive tomorrow and see how she performs.

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I just can't believe you have had 2 pumps go bad in such a short period of time. Are you sure there is not a crack or tear in the pick-up making the pump suck air? Are you sure you are orientating the pump and boot correctly so the pick-up is not getting kinked? I have had my DMC pump out in 100+ temp traffic and it doesn't even make noise.

Quote:

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Originally Posted by dvfr750f

So I have John herveys pump kit with the 'tuna can'. I tend to go thru pumps in the summer so heat is the culprit, but how?
Here is what I think.

I am getting 12.46 v at the pump when under load. The RPM relay is functioning and looks clean, but does have a slightly burnt odor to it. It does get quite hot while driving. Anyone know what the normal op temp is for this?
I bought a new pump from DMC(looks identical to Herveys pump). I installed it and after about 30 min in city traffic on a 90 deg day it began to cavitate.
I pulled over checked the fuel by removing the send unit and just sticking a finger in. The fuel didnt feel very hot. The water temp was mid way from btm to the 220 mark. I then placed a bag of ice right ontop of the fuel lines and the pump(top), let her sit for an hour then drove home. I managed to make it the 10 miles home. The pump screamed the whole way.
SOOOO, I believe it is a heat problem but not an electrical one.
I recently overhauled the entire cooling system to include a new radiator and elec fans. Before this, one of the original fans was not functioning so now the car is pulling ALOT more heat from the radiator and sending that heated air right over the tank and superheating the fuel lines and the top of the pump. I also am getting a fuel odor in the cabin. I suspect that this is the problem.
Today I fabricated an air dam out of thin sheet metal and this has removed ALL air from the radiator to being pushed over the tank. I also put a foam insulation over the two fuel lines. I will drive tomorrow and see how she performs.

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The OEM RPM relay will get very hot inside. How hot it feels on the outside case depends how long you have been running.

I've found when the fuel gets > 120 deg. F. the pump will start making noise. So check your fuel temp in the tank and see if it's that hot.

After reading through this thread you are having the exact same problems I had. Mine turned out to be a clogged pickup screen in the fuel tank. It clogged AFTER I cleaned the tank. Then it did it again a year later. Rubber was getting in the tank through the return from a disintegrating fuel line. Disassemble your baffle and check your pickup screen. If it's black change it. It think it's around $15.

Thanks for all the feedback. The fuel and the screen are all very clean. After,considerable evaluation and driving the car(with air dam installed), i believe the problem is a direct result of radiator fans blowinghot air OVER the pump and the lines. Not so much the temp inside the tank(although it does contribute). With the fix, i have no air flowing over the pump and temps are hugely reduced!

Quote:

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Originally Posted by jorge figueroa

you should use the same product used in the exhaust headers as
cover the cooling tubes in the fuel tank area
controlling the transfer of heat between the cooling tubes and the gas tank
so the fuel pump is not affected by heat and the engine will have better performance
Heat is the horsepower and performance killer.


http://www.thermotec.com/products/11...ader-wrap.html

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Finally the solution to the problem of overheating of the pump and the gasoline tank in deloreans.
Many deloreans including mine have always had this problem of having the gas pump very hot when you make a long trip around Puerto Rico. And in some cases total failure.
The problem arises from the poor design of the delorean cooling system.
Especially the tubes that pass under the gas tank. These tubes are heated by the coolant that comes from the engine to the radiator, heating the tank, gasoline and the pump to temperatures too high for its proper functioning.
As a result you hear a loud buzzing inside the car (pump too hot) and the possibility of failure.

For some time I was looking for a solution to this problem, and finally found in home depot a type of tape that is used to insulate tubes in the air conditioning system of homes or businesses. (To see photos).
It is an aluminum tape with high density foam insulation.
Using my own delorean I did heat transfer tests with one of the cooling system tubes and found that the heat transfer is practically zero.
With my delorean engine running I put my hand on the coolant pipe with the insulation and felt no heat at all.
If my hand did not feel any heat the tanks of the deloreans either

Attachment 59079Attachment 59080Attachment 59081Attachment 59082

Quote:

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Originally Posted by jorge figueroa

Finally the solution to the problem of overheating of the pump and the gasoline tank in deloreans.
Many deloreans including mine have always had this problem of having the gas pump very hot when you make a long trip around Puerto Rico. And in some cases total failure.
The problem arises from the poor design of the delorean cooling system.
Especially the tubes that pass under the gas tank. These tubes are heated by the coolant that comes from the engine to the radiator, heating the tank, gasoline and the pump to temperatures too high for its proper functioning.
As a result you hear a loud buzzing inside the car (pump too hot) and the possibility of failure.

For some time I was looking for a solution to this problem, and finally found in home depot a type of tape that is used to insulate tubes in the air conditioning system of homes or businesses. (To see photos).
It is an aluminum tape with high density foam insulation.
Using my own delorean I did heat transfer tests with one of the cooling system tubes and found that the heat transfer is practically zero.
With my delorean engine running I put my hand on the coolant pipe with the insulation and felt no heat at all.
If my hand did not feel any heat the tanks of the deloreans either

Attachment 59079Attachment 59080Attachment 59081Attachment 59082

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Very nice. I admit on hot days and long drives with the A/C on, my pump makes noise and something I would like to address. It's a shame you have to drop the tank to install though :(

Looks like a great idea but how do you get the tank back in without tearing off the insulation? Would it be better to just insulate the pipes?

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Originally Posted by David T

Looks like a great idea but how do you get the tank back in without tearing off the insulation? Would it be better to just insulate the pipes?

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It would be nice if you could slide some insulation between the tank and pipes without removing anything, but one side being adhesive might pose a problem.

I bought a custom bellypan for my motorcycle and let me tell you after installation, it was about 1/4" away from some very hot exhaust pipes. After just a few minutes, the painted surface would almsot burn your hand. I knew it would melt the plastic let alone blister the paint. I got some adhesive thermo liner and now it is cool to the touch even after sitting idling. Never thought something like that would work and it so happens I have plenty left over.

https://www.amazon.com/Thermo-Tec-14...vglnk-c1044-20

You can see just how close the exhaust pipe runs, they even made cutouts in the bottom, yet after installation of that thermo sheet, not a problem.

Attachment 59087Attachment 59088

I do hope that fixes your problem. But I did some testing and I think a major cause of the gas heating is the return fuel line. The excess fuel runs to the hot engine and is returned to the tank. I measured the heat gain from the two tank lines and the return was 1 to 2 degrees F warmer then the feed line.

Hi!
I hope my input is not too much off-topic, but as I am restoring my DeLorean #1550, which was imported 4 years ago from NY to Germany, my (original BOSCH) fuel pump changed its speed nearly every second, I bought a new one from John Herveys DAP-site just one week ago. As I read here, some people are not convinced about the fuel pumps sold on the DAP-site!? Mine did not yet arrive, but as I read this thread I´m not sure if I did the right thing...
I did not buy the one with the strange can-like baffle, but the one which is one solid module, similar to the new design offered from DMCH, but less plastic...
I would be very happy to hear, which experiences you made with THAT pump.
I hope I will not step on someones feet with this message...
Thank you, Lars.