Frustrating Fuel Problem!

[dn010]

Here we go again - I go from trying to fix my cold start valve to now my fuel pump. Weeks ago I could start my car (after pouring gas down the intake) and drive off into the sunset. I fixed my cold start valve and after that, my fuel pump wont work. It will come on after I let the car sit for a while - I can jump the RPM relay and it is on but as soon as I turn the key to engage the starter it shuts off! I unplug the jumper for the RPM relay and it sparks showing that there is voltage going to the pump, but it just doesn't run. I can take the pump out, hook it to a battery and it will run all day. What the hell? I took everything out of the tank and cleaned everything including the tank - the filter (which isn't dirty after many years-thanks John Hervey) and everything else in there.... My bulkhead connectors are clean and making contact now even though they will soon be replaced. What am I missing? I'm in this now about 5 hours and a six pack... My fuel pump is old, maybe 4 years but it has never missed a beat. I am running the one ballast resistor (everything was from SpecialT) and I did wrap up the wiring with new tape but didn't mess with any connections aside from cleaning. Any thoughts?

[TTait]

I'd guess low voltage/bad connection to the fuel pump.

Read through this thread...

http://dmctalk.org/showthread.php?1010-Fuel-pump-voltage&highlight=fuel

Check your voltage at the rpm relay, at the fuel pump with the relay jumpered, and during actual cranking...

[dn010]

I'm getting an average of 8 volts with the pump running and then it turns off - measured the voltage once off and it is between 6-7 volts so obviously it isn't enough to sustain operation. I'm going to do the suggested things in the post you linked, I appreciate it! Thanks for the help.

[dn010]

Wow, fixed already... Should have posted hours ago! I added a ground to the inertia switch and the voltage shot up to almost 12. At least the fuel tank is clean and I know the condition of my fuel system after years. I feel great now, Thanks again!!!

[content22207]

A couple of owners who run low pressure fuel pumps have been reporting pump motor problems as well. I am beginning to think their problems are also related to the inertia switch, especially since owners who have bypassed their inertia switches (I'm not advocating doing that -- just saying that they have) are not reporting similar problems with the same model pumps. The inertia switch is a troublesome ground point that sometimes even melts the harness connector.

Bill Robertson
#5939

[Bitsyncmaster]

Wow, fixed already... Should have posted hours ago! I added a ground to the inertia switch and the voltage shot up to almost 12. At least the fuel tank is clean and I know the condition of my fuel system after years. I feel great now, Thanks again!!!

Where did you add the ground?

[dn010]

Where I added the ground - I already had a good size ground wire that was running from the frame that holds the Lambda counter - to the frame of the car. I ran this wire years ago when I installed my car alarm. I forgot about this ground location - so all it took for me was a spice from the inertia switch ground wire to this location. I even had a heavy gauge wire installed there already for some reason so it took less than 30 seconds to complete this ground.

It is a shame, I think if I kept driving my D I would have much less problems, no wonder D's that sit are a mess, mine sat for almost 2 years (indoors no less!) and I'm having all kinds of issues and it was a daily driver with no problems prior.

Bill - perhaps the low pressure leads to the fuel pump breaking down... I was one of the few who - years ago - wanted to convert to a carb like you (we had many discussions about it on and off the DML), I just lacked the funds to buy a damn manifold. A ground issue is a ground issue, but I'll bet you have many less issues than us K jetters. Maybe one day.....

[content22207]

I'll bet you have many less issues than us K jetters. Maybe one day.....

Ground issues plague everybody, irrespective of fuel delivery. And while the carb itself only needs to ground the choke heater, as you can see, several owners are struggling with fuel pumps at the other end of the car. Other ground issues are of course common to everyone.

I have fewer problems because my car has a 4 gauge cable running from the front radiator bracket to the top of the engine (with a side branch to the negative battery terminal) into which every ground point is tied.

Bill Robertson
#5939

[dn010]

Ground issues plague everybody, irrespective of fuel delivery.


Hence the "ground issue is a ground issue", there isn't much you can do to escape this on a car that is exposed to elements which will corrode plus the poor ground design to begin with that I've been reading about...




I have fewer problems because my car has a 4 gauge cable running from the front radiator bracket to the top of the engine (with a side branch to the negative battery terminal) into which every ground point is tied.

Bill Robertson
#5939

I've had my frame off twice, the next time it is off (need a new frame) I will run a ground wire up like this, it is an excellent idea.

[stevedmc]

I've had my frame off twice, the next time it is off (need a new frame) I will run a ground wire up like this, it is an excellent idea.

Hearing stuff like this is convincing me to run a full length ground wire like Bill more and more each day. I have been thinking about doing it for a while but I am just lazy and have a huge to do list as it is. I don't think you need to wait until it is off the frame though. Bill did his and I think his frame has never been separated from the body.

[content22207]

I've had my frame off twice, the next time it is off (need a new frame) I will run a ground wire up like this, it is an excellent idea.

A ground bus needs to run through the interior of the vehicle, otherwise you can't tie into it (the frame itself already is a giant bus -- you just can't get to it because there's a fiberglass body in the way):
4279 4280

Bill Robertson
#5939

[Bitsyncmaster]

Where I added the ground - I already had a good size ground wire that was running from the frame that holds the Lambda counter - to the frame of the car. I ran this wire years ago when I installed my car alarm. I forgot about this ground location - so all it took for me was a spice from the inertia switch ground wire to this location. I even had a heavy gauge wire installed there already for some reason so it took less than 30 seconds to complete this ground....
Did you happen to see if your dash voltmeter indicates a higher voltage now that you run that frame ground to the fuel pump?

[dn010]

Bill - I see how you did the wiring now, seems like the best way. I was going to run a ground up the frame and tap into different areas inside the car (like I did with the Lambda counter frame) but it seems much more involved then what you have there. Thanks for the pictures.

As far as the car indicating a higher voltage - maybe slightly but...not really. My voltage runs slightly under the "13" mark so it's obvious this isn't my only issue with grounds. I've seen folks running between the 13 and 15.5 volt mark which is where I'd like to be. For the fuel pump ground I'm also using a gauge wire that is significantly smaller than what Bill is using and Dave M is using in his post (I think he used 10AWG) so once I am able to get the correct wire in there, I'll let you know my findings. I just hooked it up this way so the car would run. I am also planning on not only running a main ground wire up to the front of the car, but also one that will run directly to the engine so I can get rid of that ground strap.

[Bitsyncmaster]

As far as the car indicating a higher voltage - maybe slightly but...not really. My voltage runs slightly under the "13" mark so it's obvious this isn't my only issue with grounds. I've seen folks running between the 13 and 15.5 volt mark which is where I'd like to be. For the fuel pump ground I'm also using a gauge wire that is significantly smaller than what Bill is using and Dave M is using in his post (I think he used 10AWG) so once I am able to get the correct wire in there, I'll let you know my findings. I just hooked it up this way so the car would run. I am also planning on not only running a main ground wire up to the front of the car, but also one that will run directly to the engine so I can get rid of that ground strap.

If that frame ground fixed your fuel pump then you must have a bad ground still. I'm not sure what other things are common to that original ground. Yes I did use 10 AWG wire for my new pump ground, but that only brought the fuel pump voltage up about 0.4 volts. I did note my dash voltage gauge reads higher now (almost 15 volts) so I assume that ground was common to the dash also.

[dn010]

So far, I ran a new ground wire from my relay compartment (not hooked up yet) to the radio frame. I've crimped and soldered all the grounds from that frame to the new ground wire. This evening I'd like to finish by running a ground wire from the relay compartment to the frame (battery ground) and then from the frame to the transmission or engine. I think it would probably be a good move for me to check out the connector by the washer fluid bottle and clean the grounds on the frame extension so I'll get that done while I'm at it... I'll fire up the D and see what my voltage is once this is all complete - I'll be happy if I'm actually getting the correct voltage finally, then I can start troubleshooting other problems with one issue crossed off the list of possible causes!

[content22207]

Just attach the wires formerly ganged on the radio bracket to your bus *NEAR* the bracket. Use a nut & bolt to hold everything together so you can add new grounds to the bus as necessary (additional cigarette lighters, heavier radio ground, etc).

BTW: All those wires on the radio bracket except one are grounds in. There is only one wire leaving the radio bracket towards the rear of the car, and it is only 16 gauge -- yet another example of how badly these cars were grounded new from the factory.

If you want to extend your bus through the firewall you will need to drill a hole. The firewall is so thick, you won't need a grommet if you drill the hole the exact same diameter as your wire (solder the end on inside the car after you've run the wire through the firewall). My bus goes all the way to the front radiator bracket:
4372
(That 8 gauge wire extends the bus to the stainless bar across the front of the car, which I used as a grounding block for the two ground junctions behind the headlights. It does not have any inline connectors by the washer bottle -- if I ever need to separate the body from the car I will undo it at the radiator bracket and let it stay with the body).

Bill Robertson
#5939


So far, I ran a new ground wire from my relay compartment (not hooked up yet) to the radio frame.

Don't forget there are three ground junctions underneath the console that need to be tied into your bus (circled in my earlier pic).

My bus runs to the ECU compartment first, then branches to the relay compartment and the engine:
4371

Bill Robertson
#5939

[AdmiralSenn]

I will add another vote for the ground bus. I never really had any serious grounding problems with my accessories or fans or anything but I did notice that my voltage gauge started reading accurately after I installed the bus, and things just seemed less "quirky". It's WELL worth the effort.

[Bitsyncmaster]

BTW: All those wires on the radio bracket except one are grounds in. There is only one wire leaving the radio bracket towards the rear of the car, and it is only 16 gauge -- yet another example of how badly these cars were grounded new from the factory.
Bill Robertson
#5939

The British wiring standard does not use 16 AWG. In my endeavors into the D, the wiring seems to us 18 AWG with the exception of very high currents.

British 14 strand wire = 18 gauge US
British 28 strand wire = 14 gauge US
British 44 strand wire = 12 gauge US
British 65 strand wire = 10 gauge US

I'm going to pull my center console and find where that original ground off the crash sensor goes. If it goes to that one ground Bill has found.....what were they thinking (drinking).

[content22207]

The British wiring standard does not use 16 AWG. In my endeavors into the D, the wiring seems to us 18 AWG with the exception of very high currents.

Even worse.

Where is good old fashioned American 12 gauge wire when you need it?

If only JZD had turned to Kenosha for engineering expertise....

Bill Robertson
#5939

[content22207]

I can not emphasize enough *NOT* to forget the three ground junctions underneath the console (heat shrunk from the factory -- peel it off). If you only ground the radio bracket to the relay compartment, you haven't accomplished much (you haven't really done anything that couldn't also be accomplished by simply running a wire from that bracket to the body bolt directly underneath it.

I tied my console junctions into the bus with copper terminal lugs. Insulation was stripped off the bus wire at the appropriate places, lugs slid over it, then tightened to press the junctions against the bus. The terminal screws were lock tighted, cut off flush with the lugs, then the whole arrangement wrapped in poor man's heat shrink (electrical tape and a heat gun -- see the ring terminal in my radiator bracket pic).

I also used terminal lugs to attach the ground junction inside the relay compartment, and two smaller ones to attach short jumpers between the junctions behind the headlights and that big stainless bar (I use the bar as a ground block, just like the block in my ECU compartment).

Bill Robertson
#5939

[content22207]

These are the ground junctions that also need to be tied into a bus:

Near the rear bulkhead connectors:
4373

Bulkhead bolt itself:
4374

One inside the relay compartment:
4375

Under the console in the rear (driver's side):
4376

Under the console, in the middle (passenger side):
4377

Under the console, in the front (very close to the radio bracket):
4378

I mounted a block with a 1/4" stud in the ECU compartment to easily add new grounds, or anything I've overlooked, in the back of the car (I also have a bolt in the relay compartment, but it's 3/8" diameter -- I just use the metal superstructure, to which that bolt is attached, as a block for relays, etc).

Former radio bracket grounds are attached to the bus with a 1/4" nut & bolt. Any new grounds or anything I've overlooked in the front of the car (I am debating whether to run a new wire to the dashboard bolt by the glove box -- doesn't seem necessary at this time) can be added to the bus there.

Bill Robertson
#5939

[content22207]

Remember also that a ground bus is pretty much useless unless it has its own independent connection to the battery:
4381

Bill Robertson
#5939

[dn010]

Man, I think I would have botched this if it wasn't for these posts (or at least had this so it wasn't entirely efficient). Thanks for the pictures and all the info; looks like I have much more work ahead of me, I'll have to run to the parts house for more electrical items after work!

[content22207]

My terminal lugs came from Lowes. I think I have one left over that can be photographed (or I can take The World's Cheapest Digital Camera to the store).

Those ground junctions are most likely just like the radio bracket -- a bunch of wires in, but only one wire out. That is why I tied them into my bus.

Bill Robertson
#5939

[content22207]

A ground bus only costs about $30-$40 -- less than one single stainless steel DMC logo bauble. There is no more cost effective upgrade an owner can make to his or her car.

Bill Robertson
#5939

[dn010]

How much wire (length) do you think you went through?

[Farrar]

Don't forget that, unless you own them already, you will have to buy the necessary tool to crimp battery lugs, or a torch and solder (or both).

Farrar

[dn010]

I have a large set of crimps designed for heavy gauge wires, I think down to 4; they were around $200 bucks when I had to get them as a mechanic so those should do the trick. However, there are some connections that I would like to solder - luckily I have those tools too :hihi2:

[dn010]

Also - Bill, you used 8 gauge, Dave used 10 gauge... this may be a stupid question but is there any benefit in using the one over the other in our setting? I am using 8 gauge, but I am just curious at this point... And maybe the answer will help steer future readers while doing this upgrade.

[stevedmc]

I have a large set of crimps designed for heavy gauge wires, I think down to 4; they were around $200 bucks when I had to get them as a mechanic so those should do the trick. However, there are some connections that I would like to solder - luckily I have those tools too :hihi2:

Ouch, that sounds like an expensive tool for doing such a cheap job. I really would like to do this but don't want to fork out $200 for tools. I have a feeling someone could make a nice chunk of change selling kits for this.

[Bitsyncmaster]

Also - Bill, you used 8 gauge, Dave used 10 gauge... this may be a stupid question but is there any benefit in using the one over the other in our setting? I am using 8 gauge, but I am just curious at this point... And maybe the answer will help steer future readers while doing this upgrade.

You need to consider what voltage drop you want to tolerate.

example:
If you were not using the frame and only a buss wire ground, Your current from the front end is say 50 amps (headlights and fans). Now find the resistance of your buss wire using this table.

http://www.interfacebus.com/Copper_Wire_AWG_SIze.html

The voltage drop is equal to the resistance in ohms times the current in amps.

So a ten foot length of AWG 8 would drop 0.32025 volts.
Ten foot of AWG 10 would drop 0.509 volts.

The frame of the car has a lot of "circular mils" area to conduct current. So it's pretty good even though it's made of steel. Would be interesting to test it's resistance from the battery connection to the front of the car.

[Farrar]

I really would like to do this but don't want to fork out $200 for tools.

I thought about using a cold chisel and a hammer, but I would probably have to blunt the chisel first in order not to cut the lugs by accident -- they're copper, so they're soft.

Farrar

[Bitsyncmaster]

I thought about using a cold chisel and a hammer, but I would probably have to blunt the chisel first in order not to cut the lugs by accident -- they're copper, so they're soft.

Farrar

If your going to solder the joint you don't need the best of crimpers. The crimp is needed to hold the wires and terminal together while you solder it. You definitely can't hold your hands anywhere on the wires when soldering.

[Farrar]

If your going to solder the joint you don't need the best of crimpers. The crimp is needed to hold the wires and terminal together while you solder it. You definitely can't hold your hands anywhere on the wires when soldering.

Good point.

Here's another question: Can a soldering iron get 6 AWG cable hot enough to solder a lug on all the way around, or should I get a torch and plan on extinguishing the burning insulation later? ;)

Farrar

[dn010]

The way I'd like to complete this task will require both the torch/solder and crimp tool.

Before I got my crimp tool, I went out and got a $10 nut splitter and smoothed over the splitting wedge (these things never work right anyway). Then use 2 bolts or something on either side of the bottom to make a "U" shape for the connector (I made a steel U shaped base for mine to put the connectors in, put the connector in the splitter and then run the wire in it - n crank 'er down!

[AdmiralSenn]

I was actually able to crimp my 4ga connectors with a regular handheld wire crimper/stripper combo tool. Took some force but I got four crimps into it, two per side, then used a torch + solder to finish it off. So if you're willing to really crank and lean on a handheld tool, it will work in a pinch.

[Bitsyncmaster]

Good point.

Here's another question: Can a soldering iron get 6 AWG cable hot enough to solder a lug on all the way around, or should I get a torch and plan on extinguishing the burning insulation later? ;)

Farrar

Get a big iron or solder gun. You want at least a 100 watts or more. The higher power will solder it faster and do less damage to the insulation on the wires.

[dn010]

Get lugs with closed end connections - heat the connector with a torch and fill it with solder, then while the solder is still molten you put the wire in the lug. Use common sense though - the solder will overflow and burn whatever is underneath it so put the lug in a vice or something. If you have smaller crimp tool and need that extra force to crimp - put them in a vice and use the vice to give the extra force - again, common sense...don't go all out or your tool will break down.

[dn010]

Ouch, that sounds like an expensive tool for doing such a cheap job. I really would like to do this but don't want to fork out $200 for tools. I have a feeling someone could make a nice chunk of change selling kits for this.


I'd offer to make some of these grounds, but this wasn't my idea so it would be up to Bill and Dave, etc. If no one wants to make them - then I'll attempt.

[content22207]

Also - Bill, you used 8 gauge

No, Bill used 4 gauge. They are regular battery cables. I used four 60 inch cables IIRC. Some of the ring terminals that came on the cables were left in place, and some new ones were added (parts house sells those too). The terminal on my radiator bracket was obviously added by me, as were the terminals on the bulkhead bolt, the engine block:
4389
and the terminals that connect the bus together by the radio bracket (not pictured). Anything smaller than 3/8" was done by me. There's nothing to it. Drill a little hole for the solder to flow through, flux the inside of the terminal, stick the cable in it, heat them both up with a plumber's torch, then flow the solder in. It's no different than sweating pipe.

I'm getting ready to run a few errands -- I'll take The Worlds Cheapest Digital Camera with me to snap a pic of the terminal lungs at Lowes.

Bill Robertson
#5939

[Bitsyncmaster]

Two of the bigger trouble spots for owners (fuel pump/inertia switch and instrument cluster) are *NOT* grounded to the radio bracket. They come together in the junction behind the A/C duct, then one 12 gauge wire takes them (and a few other things) to the back of the car.Bill Robertson
#5939

Thanks for that info. I wonder what the "other things" are but that confirms my idea that the fuel pump ground was common to the instrument cluster.

Wouldn't it be great to have a harness diagram showing every wire junction location. I guess this was never a document released from DMC.

[sean]

Ground wire discussion moved here (http://dmctalk.org/showthread.php?1371-DeLorean-Ground-Schematic), please keep it there.