Mechanics

CHRYSLER LE BARON FUEL PUMP PROBLEM

1989 Chrysler Le Baron • 89,000 miles

I accidentally connected a battery charger backwards, and now it won't start. What is the most likely thing which was damaged by my mistake? Before the mistake, when the key was on, you could hear the fuel pump getting power, but now you can't hear that.
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Doa_1970
March 20, 2013.



Start by checking for blown fuses inside the car and blown fuse link wires running around the left strut tower. Pull on those wires. If they're good they'll act like a wire. If they're blown they'll act like a rubber band. There's a bunch of them. You'll have to cut the tie straps that bind them into a bundle so you can check each one. To replace them you buy new ones according to the gauge and color. They are special wires with insulation that will not burn or melt. One new fuse link wire will be long enough to be cut into two or three pieces. The length is not important.

Caradiodoc
Mar 20, 2013.
Thank you very much for your detailed response!

Tiny
Doa_1970
Mar 22, 2013.
A few more details. I tested the fusable links by putting metal pins through the insulation at each end of each wire, then using a volt meter to test for continuity, which seemed to indicate continuity, and that the fuse links are still in tact. Does that sound like a valid test?

Also, before the accident, when you would turn the key on, you could hear the fuel pump power up, but after the accident not.

After the accident, when you turn the key on, something makes a noise in the instrument panel, like a buzzing sound, and it won't turn off when you turn the key off and remove the key. You have to disconnect the battery to stop it.

Do you have any other ideas or suggestions?

Tiny
Doa_1970
Mar 22, 2013.
Yup, first of all, continuity tests with an ohm meter are valid but there's a couple of problems. Most of those links are four to six inches long. If you measured on two points between the ends the break could be outside of those points. The wire can burn open in any area. It would be more accurate to put one meter probe on the positive battery cable, then probe the regular wire just beyond where it was spliced to the fuse link.

What you did was severe overkill. Mechanics would never do that because it takes way too long and they have to charge for their time. All you have to do is tug on them. You'll know it as soon as you find a bad one. It will stretch REAL easily. You also should understand that wires were used for fuses because they were expected to never burn open for the life of the car. They feed other fuses that are going to blow when something is shorted, or from reverse polarity. In my entire career in automotive, including ten at a very nice family-owned Chrysler dealership, I only ran into two blown fuse links that other guys were struggling with. One was for a shorted radiator fan motor and one involved a wire harness that was sliding back and forth each time they shifted between drive and reverse, and a wire feeding the backup light fuse rubbed through and grounded out intermittently. Instead of going straight to the fuse links, I should have directed you to start with the dead fuel pump, then work your way back to the fuses, and to check fuse links only when everything else was eliminated.

The last thing was a big source of amusement among my Electrical students. I made a really big deal on the first day of class that they were never to poke a hole in a wire to take a voltage or resistance reading. I had over a dozen school-owned donated cars that I built real-life "bugs" into for them to diagnose. They learned how to locate easily accessible test points to do their troubleshooting. If I ever found a hole poked in a wire they had to stop their learning exercise and replace that entire piece of wire. Patching was not acceptable for two reasons. First, they had to understand how serious I was that we don't damage customers' cars that way, and second, those patches inadvertently provide clues to the next pair of students who have to diagnose that bug. When you get all the problems solved you will want to use a silicone gasket sealer to seal up the holes. I use Chrysler's gray stuff a lot but there's plenty of other good ones out there.

Also, as a point of interest, GM used a bunch of aluminum wire in the '80s and had all kinds of problems. An aluminum wire clamped with a brass rivet in the fuse box is two different metals, and when you add an acid, like road salt from the driver's feet right under that fuse box, you have the same chemical reaction as in a car battery, ... Two different metals and an acid. Sometimes people would cut the insulation on a wire to test for voltage in the dead circuit. Once the problem was fixed, within a few weeks moisture would get in that hole and corrode the wire, and they'd have the same dead circuit but a different cause. The insulation on those wires was translucent and you could where an inch or two of that wire turned to powder.

Your wires are copper and less likely to corrode but they are also sitting right where rain and road salt will spray in. Seal those babies up when you're done to avoid future problems.

Now, to get down to business, there's two LeBaron models; the GTS version and the K-car version. They're totally different. The GTS has the rounded instrument cluster with the signal lever on the dash. I have a '99 service manual with both. Unless you tell me differently I'll use the K-car version with the 2.2L / 2.5L non-turbo engine. Since we know the fuel pump is dead we'll start with an easy circuit. Current comes through the automatic shutdown (ASD) relay and it feeds the ignition coil too. A test light is more accurate for this this test but a digital voltmeter can be used. They often don't respond fast enough. Connect the grounded test light to the positive terminal on the ignition coil. Turn on the ignition switch. The light should light up for one second then go off. That corresponds to you hearing the pump run for one second. If it lights up but the pump doesn't run, there is a break in the wire going to the pump or the pump motor is open. Given the recent history, neither is likely. If you do not find voltage there for one second, go back to the ASD relay and look for it on the red wire.

There's two relays on the front of the left strut tower, and two on the left inner fender. The longer rectangular one toward the front, (closest to the battery), is the ASD relay. Remove that plug and check the red wire for 12 volts. If it's there, plug it in and feel if it's clicking when a helper turns on the ignition switch. If it's not there, check on the 12 gauge black wire on the starter relay. That one is on the strut tower closest to the brake master cylinder. If you have it there but not at the ASD relay there are two fuse links to look for. You can also just crank the engine. If it cranks we know there's 12 volts on that black wire.

Holler back with what you find so I know which way to go next.

Caradiodoc
Mar 23, 2013.
Thank you so much! You've given me alot to understand and lots of steps to try. Thank you.

Tiny
Doa_1970
Mar 23, 2013.
Thanks, I'm a poor do-it-yourself parts changers at best.
The car is a 2.5L non-turbo(K-car).
I did get the light on the Tester for about a second and then off. (Tester grounded and probe to + terminal of ignition coil)
On this car the longer rectangular relay is on the strut tower and there are three square relays on the inner fender. I replaced all the three relays from a salvage car. I had checked them as well by applying 12 volts to the coil and checking the relay spades for continuity(saw the relay make & break).
Additionally, at the salvage yard I had gotten the single board computer and replaced it( in case I had smoked the computer and hoping the salvage computer was good).
The car cranks so I didn't think from reading your last paragraph there was any need to further check these relays.
Sounds like your are going to suggest that I need to trace down the wiring to the fuel pump and/or check the fuel pump. Any suggestions on a smart way to do this is greatly appreciated. Dropping the fuel tank and replacing the pump wasn't a great deal of fun.

Thanks!

Tiny
Doa_1970
Mar 30, 2013.
First a few comments. There won't be any diagnostic fault codes. Those are erased when the battery or the computer are disconnected. The computer needs 12 volts on one wire to maintain the memory.

Any time the computer's memory is lost it will have to relearn "minimum throttle" before it will know when it must be in control of idle speed. Until that occurs the engine may not start or stay running unless you hold the gas pedal down 1/4", and it will want to stall at stop signs. It also will not give you the nice idle flare-up to 1500 rpm when you start it. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

The fact the engine started and ran proves the fuel pump, ignition coil, injector, Engine Computer, and fuse links are all okay. At this point I suspect we're looking for a different cause of the no-start now that the computer has been replaced. If holding the gas pedal down a little doesn't help, first check that you have spark, then listen for that one-second hum of the fuel pump. If you have spark but no fuel pump, it's more likely the pump is giving up. GM pumps characteristically fail while you're driving and they let you sitting on the side of the highway. Chrysler pumps almost never quit once they're running. They fail to start up due to worn brushes in the motor. You will often get them started by banging on the bottom of the gas tank while a helper cranks the engine.

If you have spark, you know you have voltage to the fuel pump because they're both powered through the automatic shutdown relay. Since it was running, you know the wiring is okay too. The only other suspect would be a loose or stretched terminal in the fuel pump connector. That is more likely to occur after it has been recently disconnected.

Caradiodoc
Mar 31, 2013.
Forgot to add that you can verify a pump problem by spraying a little starting fluid into the throttle body.

Caradiodoc
Mar 31, 2013.
Thank you again, But I think that you may have misunderstood me. The car has NOT started since I hooked up the battery charger backwards. I am Not hearing the fuel pump come on. I had changed the fuel pump several years ago when I got the car. It is a good suggestion to try starter fluid in the throttle body to see if it wants to start.
Since the test light lite when I checked it on the positive terminal of the ignition coil but I'm not hearing the fuel pump coming on is there anything else you would suggest that I check Before dropping the fuel tank to access the fuel pump?
I don't recall if I can access the fuel pump electrical connector without lowering the tank. If I can I suppose I should check to see if I'm getting 12 vdc at the connector.

I have done a lot of ill advised things on my own and I would hate to jump in to pulling the fuel pump and find out that it was Not the problem.

Thank you very much for all your help this far.
Happy Easter

Tiny
Doa_1970
Mar 31, 2013.
Thank you, and Happy Easter to you too.

You're right. I was answering a similar problem with a '96 Caravan when I started having computer trouble. I eventually was able to save my reply to MS Word, then later I pasted it here by mistake. Sorry. Now I know why it didn't show up on that other post.

If I remember correctly there's two electrical connectors on the passenger side of the gas tank so you don't have to lower it. The dark green / black wire is for the pump and it's tied directly to the ignition coil. Since you have the voltage to the coil, that leaves the splice, the dark green / black wire, its connector terminals in the bulkhead connector, the pump and its connector terminals, and the ground wire. Start at the pump connector and see if the 12 volts is there.

Caradiodoc
Mar 31, 2013.
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