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Flaky Fuel Pump


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10 replies to this topic

#1 robm

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Posted 22 November 2012 - 08:21 PM

The 1992 Loyale I bought in September when my old 1993 died still has a flaky fuel pump.

It first showed a few hours after I bought it. No amount of cranking would get the engine to run. I soon noticed that the fuel pump wasn't coming on at start-up. After several hours of troubleshooting, replacing relays, etc., I wiggled the connector on the (brand new, bought by previous owner) fuel pump and it ran again.

One guess why they sold it!

On the way home, it did it again. I plugged together the green connectors and wiggled the pump connector, away it went again.

So I replaced the pump connector. New bullet connectors, properly crimped, all taped up so they won't get wet. It seemed to help for a while, but... it still craps out now and again. Not the pump connector.

To fix it, I plug together the green connectors and wait a while. Once I hear it cycling, I let it cycle for a minute or so, then start it up and disconnect the GC's.

I have noticed that when it stops working, the relay doesn't click either. When the green connectors are plugged in, it starts to click, then I hear the pressure regs under the hood making noise and the pump at the back runs. Sometimes it starts to click right away, sometimes it takes several minutes, and a few tries with the ignition key.

What is going on here? Could it be a flaky ECU that is causing this?

Thanks.

Rob.

#2 markjw

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Posted 22 November 2012 - 09:15 PM

Next time your car won't start because the fuel pump won't come on, have an assistant crank the engine over while you pound the bottom of the fuel pump tray with a mallet. That will most likely "fix" your fuel pump and buy you some time before you have to replace the pump. Its worth a try. That has worked for me several times.

#3 robm

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Posted 23 November 2012 - 11:22 AM

It is a brand new pump. Still shiny and with original stickers showing. Pounding on it didn't help the first time it failed. I actually removed it the first time, and that didn't help. I am not sure why wiggling wires seemed to work. Just fluke.

I am leaning more towards it being an intermittent electrical fault, perhaps in the ECU. Heat seemed to be an issue initially, but it is still doing it now, when the temperature is 20-30 deg. C cooler.

:banghead: Heat may still be an issue. Last time it happened, I had the heat on, directed towards the floor. It goes right past the ECU.

Looking more and more like a new ECU is the cure. Too bad I didn't steal it from the last one I scrapped.

#4 robm

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Posted 23 November 2012 - 11:34 AM

Quote from Gloyale, on another thread, "87 GL-10 No Spark":

"The Fuel pump driver circuit actually fails commonly. There was a board member about 3 or 4 years ago who actually documented replacing the power transistor on the board to fix it. "

Sounds a lot like what is happening to me.

#5 Cougar

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Posted 23 November 2012 - 10:46 PM

Depending on what kind of injection the engine has determines how the fuel pump relay is controlled. Either it is by the rev sensor or the ECU.

#6 ferp420

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Posted 24 November 2012 - 10:57 AM

ive had problems like that with alot of different cars that sat under the redwoods to long we have a name for it out here we call it redwoodtitis also have the same problem on the coast from the salt air i get alot of free cars because of this the only thing i have found to fix it is to replace the entire electrical system or just wiggle the wires of what ever isent working and drive it over time the wiggleing will get less and less and fix it self for the most part

#7 naru

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Posted 24 November 2012 - 12:53 PM

The 1992 Loyale I bought in September when my old 1993 died still has a flaky fuel pump.

It first showed a few hours after I bought it. No amount of cranking would get the engine to run. I soon noticed that the fuel pump wasn't coming on at start-up. After several hours of troubleshooting, replacing relays, etc., I wiggled the connector on the (brand new, bought by previous owner) fuel pump and it ran again.

One guess why they sold it!

On the way home, it did it again. I plugged together the green connectors and wiggled the pump connector, away it went again.

So I replaced the pump connector. New bullet connectors, properly crimped, all taped up so they won't get wet. It seemed to help for a while, but... it still craps out now and again. Not the pump connector.

To fix it, I plug together the green connectors and wait a while. Once I hear it cycling, I let it cycle for a minute or so, then start it up and disconnect the GC's.

I have noticed that when it stops working, the relay doesn't click either. When the green connectors are plugged in, it starts to click, then I hear the pressure regs under the hood making noise and the pump at the back runs. Sometimes it starts to click right away, sometimes it takes several minutes, and a few tries with the ignition key.

What is going on here? Could it be a flaky ECU that is causing this?

Thanks.

Rob.


I`d say sticky relay,if it had not already been replaced.
Did you do the ignition relay too?It needs to be non-sticky as well.

I would use a voltmeter to check for power and ECU ground signal at the fuel pump relay COIL next time it flakes out.(ECU side of coil will drop in voltage)
Similarly for the ignition relay coil power/ground.

Might as well take a look for dirty relay contacts by comparing relay input/output voltages while you are there.(voltmeter across the closed contacts works too,should be 0 volts)

Checking pump power/ground is probably a good idea too.

#8 robm

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Posted 26 November 2012 - 11:35 AM

I didn't think there was an ignition relay. After all, GD's cure for old starter contacts in the ignition switch is to install a relay, so there can't be on in the first place.

#9 naru

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Posted 26 November 2012 - 11:52 AM

I didn't think there was an ignition relay. After all, GD's cure for old starter contacts in the ignition switch is to install a relay, so there can't be on in the first place.


Your logic totally escapes me.
The ignition relay has nothing to do w/the starter contacts.It doesn`t have very much to do w/the ignition either.

#10 robm

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Posted 26 November 2012 - 12:04 PM

Oops.

You wrote "ignition" relay, and I thought "starter" relay.

I will look into that one, to see if it is the problem. I pulled lots of relays out my old Loyale for spares.

#11 Cougar

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Posted 27 November 2012 - 04:09 PM

Another place to check for the trouble is the fusible links. Make sure they are making good connection. They are locate in the plastic box mounted on the coolant reservoir. One of them ties power to the fuel pump and ignition relays.




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