Now for a fuel related problem...loud buzzing fuel pump.

[Kenny_Z]

On Wednesday I got home with a very unhappy Delorean. I could feel the car missing under load and I thought maybe my ignition gremlin was back but when I got out of the car I could hear the fuel pump buzzing loudly. It reminded me of a fish tank filter pump that was sucking air instead of water. The summer heat has actually died down but I have driven the car more with the AC on now that my driver's window is acting up.

So today while I still had some light out I pulled the pump part way out of the tank and saw something odd. There's a metal cylinder fuel filter attached to the pump via some hoses, like the cheap ones from walmart. The hoses feel soft. There's well over half a tank of gas in the car.

My question is, does it sound like the pump is on its way out or can I get away with just John's filter kit for now?

[Delorean02378]

I'd go ahead and get the entire fuel pump kit from DMC or Rob, Travis installed one on his car today and cleaned the tank during the process. It was well worth the extra effort to clean the tank and change the filter in the baffle assembly.

I've seen and heard of too many Deloreans having issues with the fuel pump or hoses and getting stranded on the side of the road.

Kirk

[DMC5180]

I would not worry about the noise too much. Mine made horrid noises during a stop & Go parade lap at the woodward dream cruise. My fans were on almost constantly Blowing HOT air at the fuel tank. I even have the spring in the pick up hose making it impossible to collapse. It did not matter, Hot fuel is hot fuel. Once we were done cruising and the fuel had cooled down everything went back to normal.

Btw: stick with the Original baffle setup. It may seem complicated but it works just fine.

[LEVY]

I had the very same problem yesterday, found out the fuel hose collapsed and the pump stopped pumping!

Since you already stated that your fuel hose is soft, then I can tell you, you have the same problem, change your fuel hose!



On Wednesday I got home with a very unhappy Delorean. I could feel the car missing under load and I thought maybe my ignition gremlin was back but when I got out of the car I could hear the fuel pump buzzing loudly. It reminded me of a fish tank filter pump that was sucking air instead of water. The summer heat has actually died down but I have driven the car more with the AC on now that my driver's window is acting up.

So today while I still had some light out I pulled the pump part way out of the tank and saw something odd. There's a metal cylinder fuel filter attached to the pump via some hoses, like the cheap ones from walmart. The hoses feel soft. There's well over half a tank of gas in the car.

My question is, does it sound like the pump is on its way out or can I get away with just John's filter kit for now?

[Kenny_Z]

Thanks for the information everyone.

I figure if I have to buy a new pickup hose and filter (old one is missing, cylinder is in its place) then I might as well buy the upgrade kit from SpecialT. They end up being the same price and I eliminate that hose from being a problem in the future. Thankfully the tank was cleaned when it was pulled from storage before I purchased the car. I think that might be when the metal filter was installed.

[Bitsyncmaster]

The noise when fuel temp goes above 125 deg. F is caused by cavitation (my opinion). Now if it does any permanent damage to the pump is unknown but I have run a few pumps after having the noise and they ran quite a long time afterward.

[Kenny_Z]

I'm glad to hear I probably have at least a little more time with that pump. The Delorean has been very mean to my bank account lately ;)

I've ordered the kit along with a few odds and ends I wanted. I'm going to think about that air dam a little more. I may make one out of aluminum with some heat shield material. I've used some material to deflect exhaust heat on the Mustang and it seems to work great.

[David T]

I agree the noise is from cavitation caused by a collapsed or kinked pick-up hose. Happens when the tank gets below 1/2 and it is hot. The hose softens and kinks or collapses under the vacuum caused by the pump. The spring can help as can the heat dam. If the pump makes a lot of noise for a prolonged time it will affect the pump. The fuel lubricates the internal parts reducing the wear. If the pump runs without fuel it wears out. You may also need other parts like the boots so I would pull the pump and inspect the parts to see what you need before ordering.
David Teitelbaum

[Bitsyncmaster]

I agree the noise is from cavitation caused by a collapsed or kinked pick-up hose.

If that were the case, you would never have the buzz with the spring installed. I had a spring installed before and it still buzzed when the fuel got hot. I also had the hot air dam installed and still got the buzz.

Has anyone had the buzz problem with Hervey's strait down pickup?

[Chris4099]

Has anyone had the buzz problem with Hervey's strait down pickup?

I have the strait down pickup and don't have any buzzing. I originally did, but that was due to a defective pump (was very noisy right after installation). With my current standard pump (not his modern pump replacement), I don't hear it at all at idle. It's been in place several years and when idling in hot weather or in stop and go traffic, I have yet to hear it over the engine.

[Ron]

If that were the case, you would never have the buzz with the spring installed. I had a spring installed before and it still buzzed when the fuel got hot. I also had the hot air dam installed and still got the buzz.
$.02

I agree with Bitsy's thinking on the temperature- when temperature increases, the vapor pressure increases...so cavitation will happen quicker.

From Kenny's description of the hose ("soft"), I'd first suspect cavitation.
The the net positive suction head is to low (ie the pump can't get enough fuel) because the pickup is restricted, has small diameter, or it's too long (drag/lift).
It is usually described as sounding like the pump is "about to come apart inside" or "full of rocks".

But then again, from his description of the sound ("buzzing"), I'd also suspect vortexing.
It is caused by insufficient surface tension- The fuel surface is too low and/or the velocity at the pickup entrance is too high [sometimes corrected with a suction bell].
It is usually described as sounding like the pump is "growling" and usually accompanied by a whirlpool.

Now to further complicate things, we have what sounds like a makeshift pickup.
Cutting to the chase, assuming the pump is stock or a reasonable replacement, I'd pitch the pickup and never look back.

[Bitsyncmaster]

Still looking for someone (running K-jet) that has had the buzzing fuel pump with a straight down pickup. Maybe if that pickup cures the problem we can try some changes to the stock pickup.

There are other vehicles with this same problem so I would think it's not just the pickup design.

[Ron]

There are other vehicles with this same problem so I would think it's not just the pickup design.I agree.
...I hope you didn't think that is what I was saying? Kenny's, probably -- In general, no.

Dang it, now I'm wondering if the design combined with different types of gas, climate, and altitudes are why only some D's are plagued with the problem...

[content22207]

Welcome to my reality -- why do some owners have problems with Airtex pumps, yet other owners have no problems. Farrar, conversion #1, burns through them at a prodigious rate. John Marconi, conversion #2, is still running the same pump installed in 2009. Bob Babcock, conversion #7, is still running his 2010 pump, but Steve Rice conversion #8 has already lost at least one.

In our case, I am beginning to wonder if Airtex pumps are particularly sensitive to grounding issues. The stock pump ground is extremely problematic, witnessed by melted Fuse #7's and melted inertia switches. At the very least, I think every owner, no matter what kind of pump he or she is running, needs to reground the inertia switch directly to one of the body bolts (if the inertia switch is even still in the circuit -- both of my cars came with the pump grounded directly to the frame).

Bill Robertson
#5939

[stevedmc]

Cutting to the chase, assuming the pump is stock or a reasonable replacement, I'd pitch the pickup and never look back.

Are you suggesting that he use a tuna can?

[dhaney]

Related Topic: This past weekend a local owner ran into a problem while participating in a cruise with the local British Conclave. His car started to loose power was having diffculty climbing a big incline in the foothills outside Denver (roughly 6000 ft elevation) and the fuel pump was screaming like a baby in need of a diaper change! It turns out that it was an incorrectly installed pick up hose and baffle.

The owner of this particular car took his car to a local service center that has been an authorized DMC service center since the Original DMC was still making cars in Dunmurry to have a leak around the fuel boot sorted out.

We were on a road called High Grade that Bicycalist love to train on, its steep and twisty and the car was running so poorly there was no way he was going to be able to finish the tour. So we coaxed it back into Denver and into my garage.

When I took the everything apart I found that the pickup hose was facing up meaning it was up off the bottom of the tank. This means that the curved portion of the pickup hose that connects to the pump would have been facing DOWN prior to being connected to the pump and that the mechanic doing the work would have had to twist the hose 180 degrees, essentially kinking it in order to connect same to the fuel pump!

This, by some miracle, worked fine while his tank was full but when it got to about 1/2 tank on a steep incline the pump was sucking air and collapsing the hose! I oriented the pickup correctly and recoonected the pump and all is well.

Also related:
I was SHOCKED to discover just how hot the fuel was, it was hot enough that if I left my hands in the tank too long they would have been scalded! I also was amazed at how hot the air blowing in around the pump was when the fans kicked on while we still had the pump area open and the fans kicked on!

I have decided the air dam that the vendors sell may very well be a great idea and that even that may not be enough, Bitsynchmasters fuel cooler idea may very well hacve some merit and help our pumps last longer and work better.

Dan

[content22207]

Dave McKeen attributes temperature rise to fuel returning to the tank, not air from the front of the car: http://dmctalk.org/showthread.php?1560-Fuel-pump-buzzing-cure.

Bill Robertson
#5939

[Ron]

Are you suggesting that he use a tuna can?:smile:

One might perform better, while the tank was full.

[content22207]

IMHO, if an owner is going to use a Hervey style pickup, a closed bottom baffle will work better than an open bottom baffle.

Bill Robertson
#5939

[TTait]

IMHO, if an owner is going to use a Hervey style pickup, a closed bottom baffle will work better than an open bottom baffle.

Bill Robertson
#5939

The Hervey setup works very well, I have two installed and running with no problems. I originally got the setup when my new (2005 vintage) pickup hose collaped on a hot day after having been installed for less than a year (no kinks, but also no spring),

Bill may be right that a closed bottom baffle is better, I'll give it a try without reservation if I ever need to, but for now I'm 100% happy.

That said, Hervey sells it all as a kit; pickup screen, drop tube (solid), return tube, and baffle.

Most people are going to just buy the kit rather than reverse engineer the other 3 parts and use a tuna can. Once you have it, use his baffle or go with Bill's upgraded version, either way you should be happy. Just make sure to remove both the paper label and the tuna from the can before you install it.

And yes - I've had some buzz from one of the pumps even with the Hervey setup - but in fairness the temp out on the freeway read 134 degrees in the middle of I-5 (I have a temp sensor at the rock grate tied to my aftermarket mirror) and I had less than a gallon of gas in the tank. The car was still running fine but I took the next exit to get some gas. The closest gas station wanted nearly $5 a gallon so in protest I only put 4 gallons in it but the buzzing stopped immediately.



T

[Bitsyncmaster]

Owners would be amazed if they opened the tank after a hot drive and stuck their hand in the gas. Usually this is only done when the pump fails on the road.

It would not surprise me to find out the strait down pickup would reduce the pump buzz but I guess we will get a lot of data when DCS-12 is over.

When I was testing my gas cooler, I still did not get the return line cooler than the supply line so it may still need that electronic fuel pump controller. With that change the return volume would be so low (only from the FC valve) that the cooler should actually make the tank temp drop.

[content22207]

Any owner considering a tuna baffle should be advised before spending any money that the price has skyrocketed -- more than doubled in the past several years (offset somewhat by the fact that you do get to eat the tuna, unless you buy a complete pump/pickup from me in which case I eat it).

Bill Robertson
#5939

[Kenny_Z]

I was planning to start with the Hervy baffle and move to a tuna can if I had any troubles. My cats are rooting for troubles since I hate canned tuna.

Hopefully I get the parts from John before it cools off around here too much. I can get the pump to whine with a drive home from work so I should know pretty quickly.

I hope to be able to get a before and after temp reading on the gas when I install an air dam.

I'd be very interested in trying out one of these: http://www.summitracing.com/parts/FLX-4136 if I could find a spot for it. Odds are I'll never get that far.

[Farrar]

I'd be very interested in trying out one of these: http://www.summitracing.com/parts/FLX-4136 if I could find a spot for it. Odds are I'll never get that far.

I think that would fit behind the grille.

Farrar

[lazabby]

I have to throw in my .02 worth. In years past I had the issue with cavitation. A fellow Delorean owner helped me create the short drop method, similar to what is sold by Hervey. We used existing material. After that, I never had the problem again. I went one step further to address the hot fuel problem. The water hoses to and from the the radiator and engine run right alongside the fuel tank. They can be a major source of heating the fuel. If I remember correctly, didn't the factory put some rubber foam around the hoses to insulate them from the fuel tank? Anyway, I took off the fuel tank cover plate and wrapped the water lines with insulating material and put the cover plate back on. I believe that helped the issue. The air dam probably helps too but I don't have one.

[Denver DMC]

Owners would be amazed if they opened the tank after a hot drive and stuck their hand in the gas. Usually this is only done when the pump fails on the road.

I am the Colorado owner Dan Haney mentions in the previous post (p.2). We put our hands in the gas tank only ten minutes after the car died (and ten minutes after we started it again by turning the fuel pump to relieve the pickup line kink) and the fuel was scalding. I wish I had a thermometer to measure temp; I bet it was north of 140-150.

This thread is spot on as to the root cause of fuel pump failure problems. The fuel in the tank under load becomes really hot. This winter, I will re-look at the insulation of the lines next to the fuel lines, investigate a heat shield to avoid heating from radiator fans, and in the summer when the car is under load, I fill up more often to cool the tank and try to avoid cavitation. I don't have a spring in my pickup line, but I may look for one.

I would like to know if the high temp under load is most significantly influenced by incremental heating from the return line (my guess), or the radiator fans blowing heat, or radiated heat from the road, or some other factor. In my case, the fuel at the bottom of the tank was hotter than the fuel at the top, which points to the return line and incremental heating from the return line (I think,but am only guessing).

Bottom line, if we could cool the fuel temp, the pumps will last longer. There should be a standard procedure to cool fuel temp. Maybe our cars should also have fuel temp gauges.

[Bitsyncmaster]

I would like to know if the high temp under load is most significantly influenced by incremental heating from the return line (my guess), or the radiator fans blowing heat, or radiated heat from the road, or some other factor. In my case, the fuel at the bottom of the tank was hotter than the fuel at the top, which points to the return line and incremental heating from the return line (I think,but am only guessing).

Bottom line, if we could cool the fuel temp, the pumps will last longer. There should be a standard procedure to cool fuel temp. Maybe our cars should also have fuel temp gauges.

That is my guess also (incremental heating from the return line). I measured the return line was always 1.5 degrees above the supply line. Of course both temps go up as you drive the car longer. Did not measure the volume (gal/hour) of the returned fuel but with that data some fluid dynamics guy could compute it's affect. I also measured the temp when the pump would buzz and it was around 120-125 deg. F.

[David T]

The coolant pipes running next to the tank are probably the primary source of the heating with the hot air from the radiator second and the return line a minor third. Lowering the level in the tank reduces the "head" making the pump work harder and increasing the suction on the soft rubber pick-up hose. A soft hose or a minor kink because the hose is not installed right is all it takes to choke off the fuel. Without enough fuel the pump suction gets below atmospheric and the high vapor pressure of the fuel causes it to vaporize (especially when it is hot). Once the pump is sucking fumes it gets noisy because it is hydraulic (not pneumatic) and can no longer pump. Also without the liquid to lubricate and quiet the pump it gets noisey. The stock set-up is workable BUT. It MUST be in good repair (no soft hoses) and properly installed. For those who think they can "improve" the stock set-up, that is all well and good but a well maintained and installed stock set-up can be fine. One of the biggest problems I see is the hose is twisted as the pump is installed. Everything is fine until it all gets hot or the hose gets old and soft. That is when it kinks and collapses. You would be amazed at the amount of suction that little fuel pump can make! Enough to suck that hose FLAT! That is why I put a spring inside. And you must be VERY careful installing the pump to keep the hose from getting twisted. It all must be lined up before you stick the pump in. You can get a peek if you pull the sender out to check it.
David Teitelbaum

[Ron]

The coolant pipes running next to the tank are probably the primary source of the heating with the hot air from the radiator second and the return line a minor third.IMHO- The fuel filter (and lines) being mounted a few inches away from the exhaust manifold (and pluming) belongs high in that list.

Other food for thought, however significant:
-wasted pump energy from the FV and PPR is pressure => heat.
-heat from pump itself (from "useless" pumping, or not ).

[Bitsyncmaster]

-heat from pump itself (from "useless" pumping, or not ).

I agree that the electrical power of the fuel pump itself adds a lot to the heating. Another good reason to use a smart PWM controller for the pump.

[Kenny_Z]

I started up Red yesterday and within just a few minutes I heard the pump. I shut her down and pulled the pump and cheapo filter. The filter had bits of epoxy from the old filter connection lodged inside. Since I'm still waiting for Hervey's set up I bought another cheap filter, a see-through one this time, and installed it. Looks like I'm going to need to drain the tank after all to make sure those epoxy bits aren't floating around before I install the new set up. I figured the see-through filter would be a good way to check for more bits while I burn a little fuel on some in town drives. I've still got over half a tank full in there.

I see what everyone is talking about with the radiator hoses. I think in addition to the air dam I'm going to purchase some extra shielding material to put between the radiator hoses and the tank.

I'm thinking more about that finned gas return line cooler. It would fit perfectly behind the fake grill but may require some modifications that I'm not sure I'd be comfortable making. I don't want to cut into anything and not be able to return Red to stock. If I did go that route I'm probably going to be looking for a 3/8 inlet/outlet 2-4 row cooler. I see transmission coolers, do you think they would hold up to gas? This is just one that caught my eye: http://www.summitracing.com/parts/HDA-402/

[content22207]

The fake grill is a solid chunk of plastic -- no air passes through it.

Bill Robertson
#5939

[Kenny_Z]

Well...there goes that plan. I guess it is for the best. I wouldn't want to have to drain fuel if I ever wanted to take off the front fascia. Mounted in front of the radiator it is...if I go that way.

[Bitsyncmaster]

Any cooler is just installed on the return gas line. So no pressure to deal with and returning to stock is just replace the hose from the frame line to the pump boot line.