[Fuel & Emissions] The All-Fix that everyone should know...

[knt2000]

I call this the all-fix - because I believe this fix a few issues that are common - yet hard to find the reason.

First off, my car is one of the ones that takes a good 5 minutes to warm up to be able to drive it smoothly, and you can not even rev the engine at idle with out it starving for gas.

So, yesterday, I drove it a solid 40 miles for the 1st time. At about the 40 miles, the fuel pump started to cut in and out, but never stall out. It was getting worse for there on. I had to ease into 1st, 2nd and 3rd to get the pump from being under a load.

So, now I am thinking, this is crazy.........starving gas when cold, and starving gas when really warmed up.........and perfectly fine in the "happy medium" temperature ????

So, I got it home. I opened up the fuel pump area and checked it out. Everything appeared to be physically fine. I was expecting to find the fuel hoses loss or something like that. They were all fine, and all of mine are newer, so they are not cracked our dry. The rubber boot is also brand new too.

Then I started the car. I gave the revs that normally starve the engine and has the hesitating acceleration. So, that was the same. The pump was also somewhat nosier too. So, I started to wiggle some wires. Sure enough, the car shut down completely. The one side of the plug wire was also hot, and the other side of the plug was not. The side that was hot, was the one on the fuel pump side, so that tells the signal is good all the way to that point and not towards the car's electric source end. This wire was once crimped with a new wire, and someplace inside, the wire must not be getting solid electric signal. I replaced the crimp with a new wire and fresh crimp. I started the car, and did the same procedure, and it was still doing the same thing. The car even shut off when I wiggled it?!?! However, the wire was not hot...

So I looked even closer. I found that the stock DeLorean plug that I mentioned above, has play in it. It is not a solid click. Mine is not really worn too, and think it is really the style of the plug, not a good one. First thought was to buy another stock DeLorean plug, but then decided that mostly likely the new one fits like the old one - not good. So, I cut it off and wired it direct. The plug is not really necessary and it just makes a break in the wire that you could do without.

I started the car now. Not only did the car not shut off when I wiggle the wire....I inadvertently fixed the other warm up issue. The car was not running more than seconds, so I didn't warm the car up, and it would have still be a starving for fuel normally. I could instantly now rev the engine and ever thing! No starving for gas, and the car is still in it's "cold" state. It had nothing to do with the car being cold - it was because under and "electrical" load, the loose wire could not supply the needed voltage to properly power the pump.

Now the issue with it happening when the car was really warm after my 40 mile trip, that was because that "warm" wire that I previously mentioned, was most likely get very hot and caused a very low voltage to travel to the pump.

So, the fix? Get rid of the DeLorean plug on the fuel pump. Very simply to do, and cheap!

Let me know who try's this, and did it improve the warm-up issue? I may have had the loose wire in the spliced wire section as well, which your car might not. In any case, that plug is a loose fit and need to be more solid. Even if you like the idea of a plug there, change it to another harness plug that you can get any any parts store.

Here is a photo of the mod.

[Citizen]

In the photo, it looks like you crimped the wire together. While this is better than the plug, I’m wondering why you didn’t just solder the ends together, which would provide even better conductivity than the crimped wire.

I probably won’t do the mod since I don’t have the issues you have. But let me say this is a very good post, and I’m gonna try and remember the mod if I ever do have these type of probs.

Thanks for posting. These kind of posts are why I invest my time on this forum.

Thomas

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[knt2000]

Solder is something that I would have done. However, the wires are a thicker gauge and hard to twist together and solder. I have some really good crimps and are solid. I also figured around gas fumes, I did not want the electrical tape to come loose, ground out, and cause anther issue. I felt better with the crimps.

[Drew1Down]

Originally Posted by knt2000

Solder is something that I would have done. However, the wires are a thicker gauge and hard to twist together and solder. I have some really good crimps and are solid. I also figured around gas fumes, I did not want the electrical tape to come loose, ground out, and cause anther issue. I felt better with the crimps.

heat-shrink tubbing, makes a good seal and prevents water from getting in.

im having the same issue with my D when its cold it wants to die when i press the peddle, going out to my car now to check! if anything ill go out and buy a new connector (updated one that is water tight) and replace it if needed. Great post!

[dmc6960]

I'm glad this fixed your problems, but for what it's worth....

The harness plug should not have play in it. If it does then it is severely worn. New pump harnesess are available from the vendors. If it is still lose then the front harness connector for the pump could be cut off, and a replacement heatshrink-crimped, or soldered on.

Also, most cold running issues that you've described are due to a faulty Control Pressure Regulator. Have you measured your fuel pressures to verify that isn't indeed the problem? If your engine wasn't stone-cold when you restarted it's possible a CPR problem may still exist.

Just two thoughts. Good investigating with those wire temps. Sure sign of a problem.

Jim Reeve
DMC6960

[knt2000]

Also, too, the wire next to that one in my photo....that is where the signal for the low fuel and the fuel gauge. Precious experiences of my fuel gauge not working was cause my giggling that wire too - same plug! So, if the fuel gauge goes out on your car, check that plug too!

I was even told once at DMC Texas, that the fuel gauge wire gets loose and causes the fuel level of the gauge to "peg full". I think the plugs are known to be a bad design.

[knt2000]

Originally Posted by dmc6960

Also, most cold running issues that you've described are due to a faulty Control Pressure Regulator. Have you measured your fuel pressures to verify that isn't indeed the problem? If your engine wasn't stone-cold when you restarted it's possible a CPR problem may still exist.

Jim Reeve
DMC6960

My car was initially not starting very well, and took a lot of cranking to build up the gas to finally kick over and start.

I had the car looked at that was trained in these cars back then. He told me my CPR was bad, and we replaced it. That did not change anything. He even adjusted the fuel mixture to the correct measure - he said it was way off. I paid him for his time and labor and took it home. I changed the Thermo-temp switch on my own judgment, and it worked, the car start ever time, all the time now. It just still had the warm up issue while running.

[Matthew]

Originally Posted by dmc6960

New pump harnesess are available from the vendors. If it is still lose then the front harness connector for the pump could be cut off, and a replacement heatshrink-crimped, or soldered on.

I had a loose plug, so I bought a new one. Worked like a champ.

[DMCMW Dave]

Not that it's a huge deal, but this does make it something of a pain to pull the fuel pump out. There would be nothing really wrong with just replacing the plug with a matched set of good spade connectors (face them opposite ways so you don't ever hook them up backwards).

[Cory W]

Originally Posted by DMCMW Dave

Not that it's a huge deal, but this does make it something of a pain to pull the fuel pump out. There would be nothing really wrong with just replacing the plug with a matched set of good spade connectors (face them opposite ways so you don't ever hook them up backwards).

+1 on the opposite ways....you can hook it up blindfolded that way and still get it right.

I did this last year due to the same issues as mentioned above. Still fires up like a champ and have never had a pump issue since (excluding those wires to the inertia switch in the summer.....)