Electronic Fuel Pump Problems and Replacement
James Dement wrote these procedures for the first and second generation Chrysler minivans (1984-95). Many of these procedures will also apply to other Chrysler fuel injected vehicles.
A fuel pump failure will usually set no engine codes and you may get no advanced signs or warnings. Sometimes the pump will give you warning signs that it is about to go but you may not notice them until after the fact; these signs are a change in the sound produced by your pump and engine stumbling due to lack of fuel.
Replacing the pump is not usually a good time. This is because they don’t usually fail in your driveway on a nice Saturday morning, and because they are located inside the fuel tank. Yet if your vehicle happens to be on level ground, you have a good jack and take your time, pump replacement can be done by most home mechanics. Allow up to four hours for the average replacement.
First, confirm that the pump is bad by listening carefully for the one second hum from the tank when you turn the key to the start position. Don’t hear a thing? Well...., if you’ve really been living right you may want to try thumping or hitting the bottom of the fuel tank a couple of times with a large wrench or stick of wood. Don’t overdo it - just tap 3 or 4 times on the tank and turn key to start again and listening for the pump hum. On my first pump failure this got me out of a fast food parking lot only to experience the final death 50 miles later.
If rapping on the tank bottom did nothing, it might be a wonderful time to just pay someone to come out and fix the vehicle. Especially if you are physically limited, don’t have a good floor jack, and have an extra couple hundred dollars in the pocket. Otherwise consider the next step.
Troubleshooting: pump or power?
Check for 12 volts at the dark green with black tracer wire at the wiring connection located underneath the van behind the driver’s door. This wire supplies the voltage to your pump. If you have the rear heat this connector is generally found right around were the hoses are for the rear heater. There may be two connections at this location but the one you’re looking for is the larger one with four wires.
Connect a voltage meter (or test light) to the dark green with black tracer wire and have someone turn ignition to the on position. Look for a flash of voltage then off. If you get the 12 volt reading that means that the computer ( PCM) has grounded the ASD (auto shut-down) relay circuit.
Now have someone crank the engine while you are still reading the voltage at the wiring connector. If everything is working normally you should get 10-11 volts while the engine is cranking. If you only get a very brief voltage reading or zero consider additional testing of the crankshaft or camshaft sensors (or fuses). If you got any sign of voltage doing the above test but never heard the fuel pump hum, with the electrical connections intact, then there is a strong probability that fuel pump is bad and the real fun begins.
First, a word about selecting a replacement pump. If you are going aftermarket, many of the part stores will have three options: a low-end pump costing $65-$80; a “better” pump costing $85-$100, and complete pump kit assembly unit costing $130 or more. My first pump was replaced with the low-end pump. It lasted all of 13,000 miles. Hopefully the other pumps are somewhat better quality so try one of them. I’ll let you decide if you want the entire assembly or just the fuel pump itself. (It doesn’t take that much longer to replace the pump itself on your old assembly but be very careful noting how everything matches up when you take off the old pump - others seem to prefer just buying the complete assembly).
You are going to need jack stands or a set of ramps to get the back end elevated. Once it is up in the air, I’d remove the spare tire. I’ve done the job both with the spare in place and removed. There seems to be much more room with the spare out of the way and it doesn’t add much time, and it’s a good idea to remove the spare from time to time to make sure it can still be taken off and is still in good condition.
There are 15mm bolts holding the two tank straps on. If you have some penetrating oil, spray the visible threads and let them soak a moment while you go topside now to remove the four philips screws at the gas door opening. The fill hose needs to be able to move some when the tank is dropped. Now go back under the vehicle and loosen the 15mm bolts a few turns. They may be very tight the first few turns. Place a roll around jack with a piece of wood on top of it against the bottom center area of the fuel tank and remove the two 15mm bolts.
Lower the jack and fuel tank SLOWLY. I’ve found it helpful to have a four to six inch thick piece of foam, wood, suitcase, etc. to support the right side of the tank as it comes down. This is because the tank is not going to drop straight down. The right hand side is going to drop more as the fill hose tends to hold the other side up. That is OK as the pump is on the right rear area of the tank.
With the tank lowered, now disconnect the wiring connection to the top of the fuel pump assembly and remove the two fuel line hoses. It would be best to clean the area around the fuel pump opening as there usually is a lot of dirt that will fall into the tank if you don’t clean it off. I didn’t clean the dirt off on my first pump failure and it could have contributed to the replacement pumps short life.
You will see a locking ring with ears sticking up. Take a hammer and brass drift (yes I’ve used a screwdriver but working safe is better) and tap the lock ring around the fuel pump assembly counterclockwise and then slowly remove the assembly with the seal ring. Let me warn you it is going to much harder to get the new pump back into that tank than getting this old one out so try and note how everything is coming out of the tank as you remove it.
There is a hose connected to bottom of the pump. If you will look at the hose there is a pinch together connector that you can mash the ears together and pull on the pump to remove this line. If you cannot get this line off I’ve replaced the pump without removing it but you will have more work to complete in such a confined area.
It would be a good time to replace the flex fuel hoses if they’ve never been replaced. The high-pressure supply side is usually 5/16". It is VERY important that you get the correct hose. Both times the parts counter employee sold me the wrong hose - a carburetor-spec fuel line hose labeled with SAE 30R7 on the outside. Good enough for your lawnmower but not your fuel-injected Mopar. I didn’t know any better at the time and installed it. This hose developed some nasty looking splits within a year’s time and may even get soft and gummy on you. (I contacted the manufacturer of this hose and they confirmed that it was not designed for MPI application and to replace it.)
You are running 50-55 lbs of fuel pressure and need to find fuel injection hose which will say SAE 30R9! This correct hose will cost you several times as much but you are only going to need about 2 feet and then you’ll never have to replace it again. (Special thanks to Daniel Stern for documenting this information years ago — I only wish I’d known it then.)
Make sure the hose clamps are secure as this line is under high pressure and I had a leak develop when one of the original clamps wouldn’t tighten down enough. (Chrysler seems to like 7mm for bolts on these hose clamps). I changed over to the screw type of hose clamps for the discharge fuel line.
Check the round tank seal to see how it looks. Usually this seal is in good condition, but your new pump generally includes a new tank seal.
Now you can replace the old pump or the entire assembly depending on what you’ve purchased. When it is time to insert the pump back inside the tank, things get tricky as the hose running from inside of the tank makes it difficult to twist the pump assembly when re-installing. You did note carefully how it came out? Just work with it a few (many?) different ways until you are about ready to give up and then it will all fall right into place.
Tap the lock ring back till it locks into place. Then install the fuel hoses and electrical connection. Now you should be ready to raise the tank back up and bolt the straps back on. Sometimes this can be difficult depending on how much the tank has shifted on the jack and how much gas remains in the tank. I’ve been lucky in I’ve had no more than 1/4 of a tank of gas whenever I’ve done this job. Don’t think I’d try it with any more than that as the gas is going to shift on you while lowering the tank making it hard to control. [Most sources recommend siphoning off all gasoline in the tank into appropriate containers, a wise policy].
While you are raising the tank, be observe the sides so you make sure you are clearing the exhaust and brake lines. You may need to bend the lip of the tank to keep it from touching the brake lines. Check to be sure the large fill tube didn’t come out of the tank much. If it did, try and get it back near original position into the side of the tank. It was hard for me to move this hose.
Finally, replace the four screws at the fill tank door. Replace the fuel filter now, while you have the vehicle up; most pump manufacturers require a new filter for warranty. I thought my filter had a lot of contamination after only the 13,000 miles when I opened the old one up for inspection. Changing the filter is going to be a piece of cake after what you’ve just been through and you’ll feel better later knowing that it has been changed.