Help! Fuel pump continuously on...

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Help! Fuel pump continuously on...

Postby MKVII » Wed May 10, 2017 2:42 pm

Hi all,

I'm in trouble with my fuel pump. I hope you may help me to locate the problem.

Yesterday evening I came back from car wash and shut of the engine. After this, I heard remaining sound under car different from the air ride and finally found the fuel pump continued to run with ignition off. Tried a few things with the ignition key without success. So decided to just disconnect the battery over night. Next morning I reconnected battery and tried to start the car, but the fuel pump did not run. Disconnected battery again and left the car with itself for the rest of the day.

Today evening I tried start working to find the problem. At first I checked and pulled the fuel pump relay in the engine compartment, cleaned contacts and reconnected the relay. The first attempts switching ignition on and off, the fuel pump seemed to work again properly. After few trials, the fuel pump again continued to run after ignition off...! Yes, i mean ignition off! Next, I pulled the relay completely and reconnected the battery. However, the fuel pump still is powered with ignition off and relay pulled, until the battery is disconnected. What is also strange: Snorkling sounds from the CFI indicate, that pressure is not released or pump doesn't switch off, if reasonable fuel pressure is reached. Instead fuel seems to make funny sounds at the fuel pressure regulator. The sound from running fuel pump with ignition switched on should stop after a while, until the car will be started.

I should add three things: 1. The fuel pump relay under hood was replaced two years ago, because the original relay quit working. 2. My 1984 Mark seems to have a stock inline fuel pump located close to the fuel filter under car, not in tank. 3. Fuel filter was changed a while ago.

Any ideas where to look next?

The shop manual doesn't provide a solution to locate this funny kind of problem. The pump should not run with under-hood relay disconnected and also ignition off. And I would suggest, a problem with the fuel pump is more likely a non running fuel pump, instead of a continuously running pump with relay removed.

I really do not understand what's going on here...

Appreciate your help to get it back on the road.
My other car is a Lincoln.
Lincoln Mark VII Continental 1984, Corvette L-82 1979, Pontiac Firebird 1994

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Re: Help! Fuel pump continuously on...

Postby CDW6212R » Wed May 10, 2017 4:47 pm

I'd wait until John of Chris chime in soon, but I'll guess that someone has altered the fuel pump circuit. I'm not familiar with the 84 pump circuit at all, but I think they all had an in tank pump only, though it's a rare monster that John has replaced a few times. It sounds like someone has added power wiring to that external pump, and somehow the power wire is damaged/shorted to another power source. If not that then I'd wonder how the factory circuit has been compromised to let the pump run without the relay.
Don
1991 Red Special Edition, my 2nd SE, dead paint, DWS 255/45/17's on 95 Cobra wheels, and soon; DVD/Navi/backup camera, OBDII and the 347, before custom paint.
98 Mountaineer with Continental DWS 255/55/18's, big sway bars, custom brakes. Soon to be A4WD with XP8 bumpers and wing.

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Re: Help! Fuel pump continuously on...

Postby MKVII » Thu May 11, 2017 12:45 am

Thank you for your help.

Somewhere in the past and while exchanging the front relais, I found an article about the wiring and test procedure of the fuel pump and relais of the 1984, but couldn't find it again yesterday evening. My problem feels like a relais is hanging sometimes all time. However, the relais under hood is removed. As I remember, there should be a secondary relay somewhere in trunk. Will try to google the article again about the test procedure. Unfortunately, I could not find anything in the shop manual, though.

Regarding the fuel pump, last time looking under car (while changing the transmission oil), the pump found here looks very professionally mounted by a steel plate, as if it would have been grown up with the car. So we believed, it could be original.

Does anyone know about a complete list of relais part numbers and replacement types of the Lincoln Mark Vii? My local dealer here in Germany usually has some problems to find the proper ones. And this car has many of them not listed in the online warehouses...
My other car is a Lincoln.
Lincoln Mark VII Continental 1984, Corvette L-82 1979, Pontiac Firebird 1994

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Re: Help! Fuel pump continuously on...

Postby MKVII » Thu May 11, 2017 2:22 pm

Needless to say: I took the EEC relay (under hood) for the fuel pump relay (in trunk). Sorry for confusion. Anyway, pulling the EEC relay should also deactivate the fuel pump permanently, which is not the case.

Thanks, Oldschool1! I found your article about fuel pumps and part numbers for our Marks.

Just ordered new fuel pump relay...
My other car is a Lincoln.
Lincoln Mark VII Continental 1984, Corvette L-82 1979, Pontiac Firebird 1994

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MKVII
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Re: Help! Fuel pump continuously on...

Postby CDW6212R » Thu May 11, 2017 5:42 pm

That sounds promising. I knew my Mark VII's had all had the relay in the trunk, I wasn't sure if the 84 or 85 had it elsewhere, given how much changed from 1985 to 1986 up. That fuel pump relay would be my first thought if the pump doesn't shut off. The EEC relay cuts power to the computer, but the pump is activated by the ignition switch and the PCM I believe, a ground signal sent to the relay. The relay has power constantly, so if the relay hangs up then the pump would never shut off.
Don
1991 Red Special Edition, my 2nd SE, dead paint, DWS 255/45/17's on 95 Cobra wheels, and soon; DVD/Navi/backup camera, OBDII and the 347, before custom paint.
98 Mountaineer with Continental DWS 255/55/18's, big sway bars, custom brakes. Soon to be A4WD with XP8 bumpers and wing.

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Re: Help! Fuel pump continuously on...

Postby MKVII » Thu May 18, 2017 4:47 pm

Looks the problem indeed was caused by the fuel pump relay. Exchanged the relay and did a second drive through car wash without problems. The car is back on the road.
My other car is a Lincoln.
Lincoln Mark VII Continental 1984, Corvette L-82 1979, Pontiac Firebird 1994

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MKVII
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Re: Help! Fuel pump continuously on...

Postby CDW6212R » Thu May 18, 2017 9:56 pm

Excellent, keep that car going strong.
Don
1991 Red Special Edition, my 2nd SE, dead paint, DWS 255/45/17's on 95 Cobra wheels, and soon; DVD/Navi/backup camera, OBDII and the 347, before custom paint.
98 Mountaineer with Continental DWS 255/55/18's, big sway bars, custom brakes. Soon to be A4WD with XP8 bumpers and wing.

ImageImage
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CDW6212R
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Joined: Wed Feb 09, 2011 11:57 pm
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Re: Help! Fuel pump continuously on...

Postby oldschool1 » Fri Jul 14, 2017 12:19 am

MKVII wrote:Needless to say: I took the EEC relay (under hood) for the fuel pump relay (in trunk). Sorry for confusion. Anyway, pulling the EEC relay should also deactivate the fuel pump permanently, which is not the case.

Thanks, Oldschool1! I found your article about fuel pumps and part numbers for our Marks.

Just ordered new fuel pump relay...

You are welcome.
Thank YOU for keeping a Lincoln Mark VII on the road.
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