View Single Post
Old 12-26-2003, 11:23 AM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
My experience with fuel pump relays is that they usually appear bad in a "no-start" situation. They usually don't fail once engaged.

If the problem is now happening often enough to test (I drive probably 2-500 miles a week in cars rigged to monitor an intermittant failure), I would normally hook a fuel gauge (self made) that has ten feet of hard aramid fuel line (1/8in) to system pressure and set it in my lap and drive it till the problem happened. This is probably not recommended and I do have the proper way: a pressure transducer monitored by a Fluke 87. Takes too long to hook up.

Anyway, you could try bypassing the fuel pump relay and drive, but you will never know if the event would of happened. You could monitor the fuel pump signal at the pump with a volt meter while driving. This would catch the event and verify a bad power circuit (I once had a bad fuel pump circuit that was caused by a bad ingnition module that quit sending the engine speed signal to the fuel pump relay - thus causing the relay to shut off the pump).

About the only other possibility after fuel is a crank sensor. Ignition modules and coils don't usually come and go. It is possible for the crank signal to do that especially when heat related.

The idea in diagnosing is to first establish what is missing. A dwell meter hooked to the coil will verify ignition. Remember you are looking for a complete failure not just a deficiency. That is why I eliminate dist caps (possibly rotors), plugs, wires, etc.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
Reply With Quote