'97 GS 420A Intermittent Fuel Pump Issue

[JusMX141]

I'm retarded when it comes to 420A's; I'm hoping you guys will be able to shed some light on this subject for me.

My daily driver 2G has been giving me issues lately that would lead to a fuel pump problem, but it's not consistent enough for me to replace the pump and feel that will solve the problem.

This all started about a week ago, I came out one morning and started the car to head to work and it sort-of "blubbered" (misfired) and shut off. I hit the key again and it fired, but it took a second or two of me keeping my foot on the accelerator before it stayed running on it's own.

A few days passed, no other issues. I figured I had water in the fuel so I added some drygas to the tank and it seemed to fix the problem.

About three days after the initial issue, the car would not start up cold at my house. Cranks, but no start. I shot it with a little starting fluid in the airbox and it fired up, then I drove to work.

No further issues until the next morning- no start again. This time it wouldn't even stay running with the starting fluid- once the fluid goes away, it died. I check the fuel pressure at the rail, nothing. Not one drop of fuel came out when I depressed the schrader valve.

I get out my tester and check the plug at the fuel pump, there's power to the pump. I plugged the pump back in and the car fires.


I can't tell you if there's any new CEL's because the light is on constantly due to an Evap issue. I just wondered if you knew if the CAS would control the fuel pump operation on a 420A or not, or if there's some other issue before I spend $100 on a pump and have that not be the issue.

Thanks in advance!

 

[96TurboGS]

Yes, a faulty/intermittent cam sensor can play a role in weather your pump primes or not. Can you hear the pump priming when you turn the key to "ON"? If it sounds as if it's struggling when you prim it, I would suspect the pump is starting to go out. If it sounds fine I would look for blockage within your fuel system. Starting with the fuel filter (should be back by your passenger wheel) and fuel pump filter in the tank. I know I use to cheat and bypass the fuel pump relay to ground to check my fuel pressure years before I had a fuel gauge on my rail.

 

[JusMX141]

Sweet info.

Where is the fuel pump relay on a 420A? It sounds like it's under the dash like a 4G63, but I know the 420A's ECU is under the hood so it could possibly be somewhere else. If it does this again I'd like to be able to jump the relay and hot-wire the pump to rule out a cam sensor or relay issue.

 

[JVAILLAN]

on my 98 gs i had the same problem the fuel pump would not prime when the engin was cold . it was a mane ground at night it would get wet and not ground . its a black plug next to a gray plug on the fire wall by the brake and clutck oil.check the black plug thats all it was for me just a dirty plug. hope it work out for you.

 

[96TurboGS]

Sweet info.

Where is the fuel pump relay on a 420A? It sounds like it's under the dash like a 4G63, but I know the 420A's ECU is under the hood so it could possibly be somewhere else. If it does this again I'd like to be able to jump the relay and hot-wire the pump to rule out a cam sensor or relay issue.

It may also be a good idea to clean the both crank and cam sensor harnesses free of debris, that tends to help often. If it's a manual trans. there should be 2 black boxes near the windshield washer reserve on the driver's side. (The fuel pump would be the right black box) However, you may find it easier to tap in though the ecu harness where all the wires are. There should only be one wire that's white with a red stripe, that's the wire to ground. The Fuel pump relay is always hot, so it should prime (when you ground) with or without the key in the "ON"/"Start" position.

 

[JusMX141]

Fuel Pump is definitely not the problem.

I'm moving on to the ignition switch, then ASD Relay, then cam sensor, then crank sensor, then ECU in that order as recommended by a Chrysler tech at my local dealer. I'll post back with my results.

 

[JusMX141]

Fuel Pump replaced, Ignition Switch replaced; the problem still persists.

New symptom today, the car acted up for the first time when hot. I was at a restaurant for about an hour, when I came out the car started and shuttered, then shut off. When I attempted to restart, I noticed if I didn't touch the accelerator the car was fine. It idled fine, but if you even TOUCHED the throttle, the car would try to die. A couple cycles with the key switch and the car fired and ran fine.

I'm leaning toward the cam sensor; can anyone give any more insight? I'll post results either way.

 

[JusMX141]

Fuel Pump replaced, Ignition Switch replaced, Cam Angle Sensor replaced, ECU swapped with a known-working unit. The f*cking problem STILL PERSISTS.

The only fuel control sensors left to be replaced are the crank sensor and the MAP sensor.

 

[96TurboGS]

Is there any way you could get to a snap on scanner (or some sort of logger) that you could use to view all of your sensors values? (map, iac, cam, crank, iat, clt, tps) I think it would help you a lot more than taking the shot gun approach. Looking at the long term fuel trims is very helpful, as if its way off it could affect start-ups. Another easy, inexpensive fix is the fuel filter as I've mentioned before. Did you ever find out what your fuel pressure was at the rail? It should be around 45-50 psi. Does the car act up when driving, or is this only during start-ups?

 

[JusMX141]

I believe I've found the problem.

It took replacing both the Fuel Pump Relay and the ASD Relay with new ones for the problem to completely go away. I had tried replacing just the fuel pump relay at first and that didn't help, then swapping that one new relay to the ASD slot and the problem still persisted.

For future reference, if either of these relays are suspected to be giving you problems, replace them both. You don't even have to half-ass their replacement with Radio Shack relays....a quick cross-reference of the OEM Chrysler relay number (4671047) turns up a RY479 Standard Motor Products part number which is a direct replacement for the factory relay at a whopping $10.95 each. It even snaps on the OEM firewall hanger.

Thanks to everyone for enuduring my lack of 420A knowledge.