1996 Dodge Neon Fuel pump/PCM issues

AJRUTHERFORD

MEMBER
1996 DODGE NEON
4 CYL
2WD
MANUAL
144,000 MILES

This one gets a bit complicated, so we'll go back and forth I'm sure. A few months ago my car started hitching and stuttering really badly. On my way to get the system scanned the car died completely. The engine turns over, but I was getting no fuel. After going to replace the fuel pump, I found enough rust on the tank to warrant replacing the whole unit (I'm not giving up my car. I can't afford another one).

Before going further I have to say that I could not find a new metal tank that also had the nozzle to connect the neck to the tank itself, and mine broke when I went to remove it, so I switched to plastic. I thought this would be possible since the fuel filter/pressure regulators are both types are non electric and fitting the systems together seemed very doable. The pump is used (it came in the tank, but seemed to work fine).

When I installed the new tank/filter/pump and put a couple gallons in, I turned the key and heard the new pump kick in for about 1 second, then shut off. Tried turning the key and I still get turnover, but no gas. A second check of the fuel pressure shows nothing. I checked the line all the way back to the fuel pressure regulator and the whole thing is clear (I used an air hose). The PCM in my vehicle has died in the past and I'm suspicious of it now, since it's not throwing errors anymore.

So ultimately the question is: where should I go now?

5 Replies

CARADIODOC

MECHANIC
33,916 POSTS

Hi ajrutherford. Welcome to the forum. Now that you played with the fuel system, have you checked for spark? Since the pump is running for one second then turning off, that system is working properly.

What do you consider "rust" on the tank? I heard of mechanics in Washington being afraid to work on a Wisconsin car due to surface rust on the tank. Here in WI, that is normal for a one year old car.

Caradiodoc

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Thursday, July 15th, 2010 AT 4:40 PM

AJRUTHERFORD

MEMBER
6 POSTS

Thanks for the response.

By "rust on the tank", I mean "the ring broke trying to unscrew it and two of the teeth fell out prying the remains away to get the fuel pump out". That kind of rust. It's why I switched to plastic.

In regards to the fuel pump, I'm concerned that I'm not seeing fuel at all coming out of the tank. I placed an oil pan under the fuel pump and disconnected the hose from the fuel pressure regulator and turned the car on. Again, I hear the pump kick in, then shut off. I never saw a drop of fuel. That's my problem; I'm not getting fuel. Of that I'm absolutely sure.

I did do a spark check with my wife turning over the engine and I'm seeing sparks on all four plugs. I did a resistance check on the cables and they were all sitting around the same number of ohms. I don't know how to check the cluster, but I think it's okay since I'm getting sparks.

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Thursday, July 15th, 2010 AT 7:21 PM

CARADIODOC

MECHANIC
33,916 POSTS

Dandy. The most common failure is loss of fuel AND spark. A lot of people get wrapped up in the first thing they find missing and forget to look for additional symptoms.

On Chrysler vehicles, the fuel is first pumped into the tank the pump sits in. Fuel is drawn from there to be sent to the engine. That prevents the common GM problem of fuel starvation on corners when the level is low, and it helps to cool the pump motor.

Is it possible the pump simply hasn't run long enough yet to get fuel up to the engine? After that initial one second burst, the pump won't run again until the engine computer sees engine rotation, (cranking or running). During cranking, the battery voltage is lower than normal which will slow the pump a little and reduce its output. The easiest way to work on this system is to bypass the pump relay so the pump runs continuously. This could mean jumping the separate fuel pump relay if there is one, otherwise jumping the automatic shutdown (ASD) relay. The fastest way is to just pop the cover off and squeeze the contacts. If you want to use a jumper wire in place of the 1" square relay, look at the five terminals on it. Disregard the two parallel ones on each side and the center one. That leaves two terminals that form the letter "T". Those are the two to jump in the relay socket. If you have the smaller 1" x 3/4" relays, it's the same terminals but instead of forming the letter "T", the top of the "T" and the two parallel terminals are all three in parallel. The center and bottom terminals are turned too so in effect the terminals you want still form a T but it's upside-down compared to the other relay.

You can jump these contacts with the ignition switch turned off. With the pump running, disconnect the hose at the fuel filter and other points to see if you can find that elusive fuel.

Caradiodoc

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Friday, July 16th, 2010 AT 2:36 AM

AJRUTHERFORD

MEMBER
6 POSTS

The bypass made for a great diagnostic tool and pointed me in the right direction. I ran the system for over a minute straight without a drop of fuel, so I dropped the tank and pulled the fuel pump (ugh). The thing was so clogged with oil that it couldn't draw fuel (it also ruined the gas I had put in). New fuel pump and another bypass to get the fuel up and the car fired up. I appreciate the help.

Also, the switch from metal tank to plastic (and the change in fuel filter and pump and connectors) didn't seem to bother the system. I don't think the car sees any difference, so this can be a major time saver in the future for people who need a new system and can't find the replacement parts.

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Sunday, July 25th, 2010 AT 8:33 PM

CARADIODOC