A long running issue with the DeLorean has been the fuel pump becoming noisy whenever the fuel in the gas tank becomes too hot. I've seen this topic posted many times here on the DML. Before you know how to fix anything, it's always a good idea to know first what is causing the problem.
The fuel pump itself is suspended from the top of the gas tank. Bolted to the bottom of the gas tank there is a baffle which acts like a sump to collect fuel for the pump to feed the system. Connected between the two is the fuel pickup hose. Since the hose sits in gasoline, it's resistant to gasoline. This is also it's downfall. Since it is made out of a soft rubber it is easily colapsable. More so the hotter it gets. When the hose collapses it begins to starve the pump of fuel. This is what causes the fuel pump to buzz. The more the hose collapses, the worse the noise gets. I have had my car "buck" in traffic because the engine was so starved. Traditionally there have been 3 common "cures" for this" 1. Install an air deflector behind the radiator to keep hot air away from the tank. 2. Fill the tank with cold gasoline. 3. Ignore the sound. None of these fixes were optional for me. I live in the desert, so in the summer time all the pumps here dispense hot gas. Plus I've been told that the air defector can cause a vapor lock at speeds of 65+ MPH thus killing engine cooling. Besides that, it would restrict the exhaust of the radiator. As it is right now, hot air flows over the tank and out the front wheel wells. And I couldn't just ignore the sound. Even with all these suggestions, there still wasn't a cure to fully prevent the issue. Only ways to lessen it. I did search for a replacement hose, but all were of the same grade. Harder hoses were simply layered, and would seperate with the same results. Stainless braided hoses were not acceptable either. All the versions that I saw had a paper layer between the braid and the rubber. Not only would the internal hose still implode, but then I'd have paper and glue in my fuel.
When this topic was raised once again on the DML, David Teitelbaum mentioned in one posting that he had used a spring to keep the hose from collapsing. After a couple of e-mails with the details, I went ahead and performed the modification with great success. Here is how to perform the mod yourself.
ONLY PERFORM WORK ON YOUR FUEL TANK IN A WELL VENTALATED AREA AND WEAR THE APPROPRIATE GLOVES WHEN COMMING IN CONTACT WITH GASOLINE! This warning is both to prevent fire hazards, and for your personal health.
The spring itself is a screen door type available from Home Depot. The size is: 9/16"x16-1/2" .054
1. Drive you car to use up as much fuel as you can to lower the amount in the gas tank. Let the car cool off.
2. Disconnect the battery
3. Remove the carpet, spare tire, and the access panel to the fuel pump from the trunk.
4. Remove the fuel pump. Disconnect the electrical wires, remove the large clamp, and the fuel pickup hose from the bottom of the pump. Note: Tuck the harness wires for the pump between the wires for the sending unit to keep them from falling down.
5. Drain the fuel tank. Note: The quickest and most safest way to accomplish this is by running as "shaker", or self-siphoning hose under the the trunk, above the tank and out of the right side wheel well into a gas can.
6. Remove the fuel baffle from within the tank. The best way to accomplish this is to unscrew the nut and washer that hold the baffle and it's assembly in place. The baffle should pull out with relative ease. Just rememeber not to bend the metal retainers.
7. Disassemble and clean all parts of the baffle.
8. Side by side measure out the fuel pickup hose and the spring side by side. Using a pair of heavy duty wire cutters, cut the spring a little shorter then the length of the hose measured from between the two 90º elbows.
9. Place the spring into the freezer, and soak the hose in hot water for about 2 minutes or so.
10. Pour dishwashing liquid into the hose and rotate to get a good coating.
11. Insert the spring into the hose. As you progress, you will need to occasionally resoak the hose in hot water, and pour more liquid soap in. Just be sure not to get any of the soap on your hands so you can maintain a tight grip. This will require a little bit of time, and alot of patience. A sink lip makes for the best place to push on the spring. Once the spring is about ¾-½" from the end, pull the rest through with a pair of needle nose pliers.
12. Pull the spring to stretch it out. Cut off how much you don't want, and then tuck the rest back in. Make sure that you bend the sharp end of the hose in twards the center of the hose. Do this on both ends.
13. Flush the hose out with cold water for 20 minutes.
14. Reassemble the baffle. Note: If you have a difficult time getting the hose the slide back in through the grommet on the baffle, use a little soap. Just remember to flush afterwards for 20 minutes.
15. Dry the hose (and baffle if applicable).
16. Attach the prefilter screen to the intake on the hose inside of the baffle.
17. Reinstall the entire baffle assembly back into the gas tank. Here's the quickest way how: The bottom half of the baffle has a slit in it that the toungue of the upper half will slide into. Now both pieces will snap together. Next the bottom metal retainer will attaches by way of it's ends being inserted into the two widest drain holes on the bottom of the baffle. The loop on the retainer sits on top of the baffle toungue where the bolt in the tank slides thru. With the bottom retainer in place, unsnap the front porttion of the baffel. This will make the baffle less riged, and you can squeeze it to clear the opening. Once inside, push the baffle against the bottom of the tank, and it will snap back together! Install the top retainer, the washer and the bolt, and you're set! If you have a hard time installing the nut and washer, try this: Wedge the washer between the top retainer and the bolt. This will hold everything in place long enough for you to install the nut.
18. Reinstall the fuel pump. Take care the when you attach the pick up hose that you twist it that much when mounting the pump. Also make sure that you clip the fuel return hose into place so that it will pour directly into the baffle itself. This will insure that the filter screen stays submerged at all times. Note: When remounting the pump, don't let the fuel hoses rest against the underbody. Make sure that the wires that go between the rubber boot and the cover and seated into the niches for them. And make sure the cover is bowed upwards instead of down.
19. Tighten the clamp to seal the pump.
20. Fill the tank back up.
21. Reattach the battery cables and you're ready to go!
Since performing this mod, my fuel pump has run quiet ever since. I've had the car out in 89ºF weather, with less then ¼ tank of gas, driving up steep hills bottoming out the gas gague with the pump silent as ever, and no performance problems.
Also, the fuel tank is not something that you want to always open up, especially when acessing the baffle. If you've come this far, you now know why. That's why I reccomend the installation of a new prefilter screen. The screen is attached to a barbed fitting using some sort of resin. When I removed the screen on my car the resin crumbled. Needless to say I now have debries at the bottom of my gas tank. Rather then use an original screen and risk more of that resin in my tank, I opted to pick up a prefilter screen from Car Quest. To attach it to the barb I used some Bondo Marine Epoxy. It comes in a putty form, and says on the label that it's resistant to gasoline.
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