96 cav 2.0 start/run problem

freind of mine bought this car and a few weeks later going down the highway it started to miss badly.the car has 200k+ and was working fine up until then.the car would start and run but #1 cylinder was not firing.that's what local shop said when he stopped there to have them do a quick diagnosis.i suggested replacing coil as spark was almost nonexistent.so we removed coilpack @#!@$!E% and changed both coils as they looked original.and just to make life easier,remounted coilpack on front of engine!!!!by simply cutting insulating wire cover to allow wires to be pulled to the front.simple really!mounted it by 1 hole on backing plate to trans stud lower front of engine!car started and ran great!end of stor........wait!!!took car for test ride down street and back.everything ok!park in driveway and leave idle(it originally had a really low idle!)and car slowly died out!would not restart.would almost start but not catch.why? determined that fuel pump was not running!did some electrical checking and it all seemed ok.came to conclusion pump had died!came back next day to confirm electrical checks and car started!ran it for a few minutes and it died when allowed to idle down.would not restart.pump not running.came back next day but car did not start.did some more electrical checks and found corroded connections at fender fusebox and battery body ground.cleaned and reconnected.checked battery connections too.car started right up after this work!!!drove to gas station a few miles and then on way back car just died on road!!!towed back.fuel pump not running.did wiring tests and confirmed juice getting to pump plug on tank!checked for ground at plug on tank.shows good.but tank plug has a lot of wires so not sure if ground is for pump.it's a black/white stripe wire?light grey for hot?car would not start.back to defective pump theory.next day car starts and runs on second cranking attemp!probably because we opened filter day before and checked fo any flow.thus depressurizing system.have basic fuel electrical diagrahms and test procedures and since the car has 200k and has 5/w30 oil and it gets mighty thin at temp and diagrahms indicate an oil pressure to fuel pump relationship i'm thinkin the oil pressure switch is shutting down the pump?that might explain the idle die out but not the on the road die out?or the pump is just getting warm and failing?or more unfound corrosion in the wiring system?but tank plug check says it's ok?i also noticed this car has a defunct alarm system still integrated?aftermarket i think?he called me today and said car started and ran and he let it run for a bit and shut it off and it restarted and he then shut it of and got a ride to work.tank does not look like it has any signs of it being removed in a long time,maybe original.i was thinking why not just change pump anyway with boneyard piece and see if that's it?seems to be the cheapest guess right now?would like to get definite wiring color code at a tankplug definitions!!!:evillol:

A boneyard fuel pump! Hopefully you can find one with verifiable Low mileage,otherwise why bother . I`d get the pressure checked before doing anything . I think I`d swap the filter as well even before checking pressure

You said the Mech said that the #1 plug was not firing....Did he get a code ??? PO301 ?? ... How did he know the spark was weak ??? Did he measure it with a spark gap tester ??

That would mean any of the following conditions.....Faulty spark plug or wire,
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

My guess is the coil are good and you had a fuel issue from the beginning !!

Perform a fuel pressure check before and after changing the filter !!!

Also read this....it MAY apply.....

As soon as you turn ON the ignition switch to start the engine a 2 second battery voltage signal is sent from the computer to the fuel pump relay and from the relay back to the fuel pump in the fuel tank.

Once the engine starts, The computer BYPASSES the fuel pump relay and now sends a constant contionous battery voltage from the computer to the oil pressure switch of which is now CLOSED because the oil pressure is UP because the engine is running. Therefore the battery voltage flows thru the oil pressure switch back to the fuel pump to run the fuel pump constantly until you turn OFF the engine.


What I would be looking for is a corroded or loose electrical connection at the oil pressure switch or at any of the electrical connectors from the oil pressure switch back to the fuel tank.

There is also a SINGLE BLACK GROUND wire that comes off of the fuel tank wiring harness near the fuel tank and is GROUNDED to the vehicles frame. If any of these circuits are loose or corroded it will start to cause a VOLTAGE DROP to the fuel pump of which will shut down the fuel pump until the circuit COOLS OFF.

JzJzz ....and the Man from Down Under...Cheers Mate !!! Fosters Rule !

GAWD!!!!!!!i typed a really long detailed reply and the forum ate it cause i took too long and had to log in again!!!!!car is running with boneyard pump!i also replaced plastic lines with rubber ones!now i could cut hole under back seat and extract pump from there!tank came out fairly easily though!also when i took out old pump,it failed testing thru electric plug but ran when i tested directly on brush holders!all plugs in circuit checked clean!i might disect further?decided on boneyard pump because new cost over 250!!!!and thanks to all who responded!great info!:grinyes: