Monday, December 14, 2009

Gremlin Hunt / Fuel Pump Area Upkeep

This posting starts off with the picture above for several reasons.
  • First, and most relevant to this site, is that the picture represents 2109 (on left) out for a reliable and spirited weekend morning ride, after being down for the previous 4 weekends, until a malfunction was corrected.
  • Secondly, it is pictured next to my friend Mike in his DeLorean, which he recently got back on the road, and it is the first time both our cars were out for a drive together.
  • Lastly, the picture was taken from my son’s (who was down for Thanksgiving) ’85 Supra, which is a cool car itself, and it represented the 3rd car of that weekend’s impromptu 80’s car cruise.

The Gremlin Hunt
Back to the blog posting, 2109 was down for 4 weekends, as I chased down a gremlin which was causing the car to at first buck, then stall, while driving. The stalling was as if someone reached in and turned the key off, as the car would restart just fine after it would stall. It got progressively worse where it would happen after 30 minutes of driving. The issue felt like an electrical problem, so it was time to chase it.
My approach would be to start at the fuel pump, and finish at the engine bay, on all related components. I knew that working only on weekends this would limit me to driving her until it was fixed, but I also knew that this meant that certain older untouched (by me) systems would get addressed.
In the order of attack, I would investigate and repair if required:
  • Fuel pump
  • Fuel pump connector (previously identified as a “connector of interest”)
  • Grounds for fuel pump.
  • Fuel pump connections at washer bottle.
  • Inertia switch & wiring
  • Fuse box area
  • Ballast connectors
  • Ignition Coil
  • Ballast resistor & wiring
  • Distributor cap & rotor
As expected from a car that at this writing is 28 years old, at each step above, something suspect was found, and then was corrected. In this posting I will only cover a few of the items above, and discuss and show what upkeep was done to those areas, which you may wish to consider for your car as well.

Fuel Pump Area
Since the symptom was the engine just stopping, the fuel delivery system, specifically its wiring, became suspect of possibly cutting out power to the pump, thus causing the engine to starve for fuel.
I must confess at this time that when I first got 2109, and was looking at references for parts replacements, the subject of anything to do with fuel, and work on fuel related parts was intimidating to me because of the respect that I had for working with gasoline - in my home garage. The project below became my best medicine to cure me of all the intimidation. I suppose the trick, for me, and what I recommend, is to not rush work in this area, and to take proper preventative safety measures.
And those measure are: Be respectful of working in this area, you are dealing in a potentially high combustion area, do take the proper precautions such as taking the battery offline prior to commencing the work, and having no spark or flame producing items near this work area. Also protect your hands from contact with fuel, and work in a well ventilated area.
Starting Point, Fuel Pump Area

The picture above, was when I first opened the access door about 20 months ago. This was uncharted area for me, since then except for the tank nearly everything there has been replaced today.
Before this Gremlin hunt, I had previously:
  • Replaced the original fuel sender for an updated one, then wound up putting the original back on (a story for another day)
  • Changed the fuel boot cover (discussed below).
  • Changed those orange fuel lines which were beginning to get brittle where they met the hard lines. This was producing a gasoline smell when the car was in the garage, so I took care of that promptly, and it did solve the fuel odor issue. For the replacement lines, I used new fuel hoses rated for high pressures.
  • Covered the AC hoses nearby with some pipe insulation to prevent them from rubbing on the access panel.
By the way there are some excellent looking fuel hose replacements available from Martin G. at Delorean, for $105 shipped anywhere. They come new fittings pre-crimped, as well as with a stainless dome nut and copper washers, for the fuel pump. Here is a picture of them, more information at his site:

Fuel Boot Cap
I’d previously had the boot cap off the fuel pump area and when I did, I noticed that it was very soft and it felt like it was thin and could easily puncture it. Months earlier I had ordered from Don Stegar's DeLorean Motor Center in California, their replacement boot which sells for $29.75 and has gotten some positive remarks from other owners. This replacement boot feels noticeably thicker and sturdier that the one that came with my car, and as I understand that it is less susceptible to fuel rot due to the ethanol mixes we are all currently having to purchase.

106684, Upper Fuel Pump Boot
DeLorean Motor Center, CA.
Another interesting feature of this new boot cap, is the the fact that the hoses that come out of it are a very tight fit. It took a little silicone spray to be able to force and pull the fuel hoses through them ... which is a good thing because they remain very secure and water tight, as installed.

Fuel Pump
Since the symptom was the engine just stopping, the fuel pump became suspect of possibly cutting out. I searched 2109's maintenance records (available since 1981) and found that I was running an 8 year old pump, which as about 15,000 miles – the age and miles weren’t terribly bad, but I figured that a refresh here may not be a bad idea, worst case is that it did not fix the issue, but at least I would have a new pump and good spare.
The pump came out fine, looking in great condition for its age.

Fuel Pump Baffle, Screen, and Pickup Hose
After the pump was out, the baffle remained inside the tank and was very easy to remove.

Referencing the service manuals and online parts catalog, my baffle was missing one set of hold down wires, and the bottom circular part.

That bottom part is important, because in effect instead of the baffle forming a drain cup to collect returning gasoline, without the bottom it was more of an in-place open collar. I suppose under low fuel conditions, this would cause fuel starvation, and especially with low fuel at an incline. On this topic, Dave Swingle from DMC-MW stated on DMCTalk, most of the early VIN cars did not have the bottom of the baffle installed, as he has observed in servicing them. I suppose that it is possible that the part was not available for early production, and the factory decided to proceed builds without them. Contact your nearest DMC franchise for availability, should you also be missing one.
At this point, also check your pumps filter screen. at the bottom of the baffle, at the end of the hose. If it looks dirty, a replacement ("improved part") can be ordered through DMC (#101643, $18.95).

SpecialTAuto also has this part (#101643, $18.95) shown below. They also have a custom filter application that bolts immediately under the fuel pump, and eliminates the need for the pickup hose, but I chose to keep the stock functionality with the pickup hose attached to the pump.

The baffle system was reconstructed with the new bottom, and the existing hoses were re-used as they were in good condition. Evaluate your car's hose, you don't want this hose, which it has been known to, kink inside the tank. Also important note: I made the mistake of thinking I could buy regular fuel hose, but that is not recommended as this hose will be submerged in fuel and most parts store fuel hoses are not. Again, if you need ot replace, this is an available DMC part (#106286, $19.69 - not a NOS part).
The reconstructed baffle system is shown below. It does not go in as shown, the circular bottom drain part needs to be off to clear the the tank opening, and is then reattached inside the tank - trickier that it sounds, but very doable.

Fuel Pump re-Assembly
If you wish to replace your fuel pump, you have a surprising amount of choices for our cars. There are two options from two vendors.
DMC will sell you a NOS pump (#11085, $139.):
...or a newer "after market" pump (#11085A, $99)

SpecialTAuto has new Bosch fuel pumps ($134.95)

...and a new higher flowrate pump (#$89.95):

I like the fact that this one comes with those protective boots, for the electrical connections.
An unexpected surprise was how corroded the hard return line was. This is a uniquely bent tube that sticks out of the pump cover, sort of wraps around the pump, and is where the submersible fuel hose that feeds into the baffle cup, attaches to. Being a regular steel tube, mostly suspended under fluid for 28 years, I suppose it makes sense it would not look too fresh. Fortunately DMC (#105020, $24.95) and SpectialTAuto (#$44.95) both sell a stainless replacement, which are excellent “while you’re there” mini-refurbishments (SpecialTAuto's price also include a stainless fuel pump metal collar ring).
A few other things to check, or consider to upgrade in this assembly are the fuel pump boot, the lower part that goes inside the tank (DMC #101391, $54.50), the pump's wiring conector , as well fuel pump's fittings. In my case, I could not remove the fitting from my original pump (remember you'll need two copper crush washers), so I ordered a new one for the new pump. It's probably a good idea anyway leave the original fitting on, so in case an emergency spare is needed, it will already have it's fittings (and washers) pre-installed.
Below is the re-assembled fuel pump assembly, ready to drop back into the gas tank.

Putting it back in is a little tricky the first time and definitely requires some trial and error. The trick is to have it drop in the correct orientation, where:
  • the return line inside the tank will not kink,
  • where the fuel pump connectors are close to the mating harness connector,
  • that the return line does not stick up too much,
  • and that the supply and return lines are oriented just right so that their matching hoses line up correctly.
You'll figure it out what works best, just takes a little patience.

Fuel Pump Wiring
The last item to look at in this area is the harness connector to the fuel pump. This is a two wire plastic plug that on my car had exposed wiring just going into the crimped connector pins. Additionally the wiring just beyond the connector was brittle. I took the opportunity to correct all this by disconnecting both the fuel pump and fuel send connector, and pulling from underneath the car (easy to do, of course with the spare out). I did this so I could solder at a distance from the gas tank. I soldered a new set of wires directly to the pins, then spliced a good 18-20 inch section into the existing harness.

The above work was done on spare weekend time, did it solve my engine stalling issues? No.
So this meant that a) as stated earlier all changes done represented good upkeep in this area, b) I know now that I have a good working spare pump (with fitting), and c) I would have to move on to other components. I am publishing above my component research, findings, and fixes, so that you have a reference to consider checking the fuel pump area as a future project, and/or as a preventative measure. This is by no means a comprehensive fuel system update to the car, to take it further it would have also replaced the accumulator (previously done), the external fuel filter, and the injectors (also previously done on 2109).
There were a lot of different parts mentioned here, mostly available from either DMC or SpecialTAuto. These of course can be bought as seperate parts, but check with both vendors as "kits" with many of the parts mentioned are offered by both vendors.
Picture of completed fuel pump job.

UPDATE 05/18/13
So, reviewing this posting I should note that (if you didn't know) there is a completely new Fuel Pump solution by DMCH.  It is a very modern fuel pump that integrates the fuel sender as well.  All information today points to a great new product.

Ordering information here:

If you have a few minutes, be sure to check out the "Best of" postings. Thanks.


Anonymous said...

These are the same exact symptoms my car is exhibiting. I think the pump just failed permanently (in the past it has come back to life). But I'm not sure that is the original problem relating to bucking and dying.

Any idea which thing actually fixed your problem?


Ozzie H. said...

Good question. I had covered it in details at the forum, but since all the data there was lost...
As it turned out, the cause of the original symptoms was the ignition coil. Once I replaced it, car was good as new.