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Old 04-04-2008, 04:48 PM
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Join Date: Jun 2004
Location: South Louisiana
Posts: 48
Question 89 420 died today

Please Help.

Our 89 420 was running perfectly this morning until we stopped at a red light. When the light changed to green I hit the gas pedal and the 420 took off as usual. 25' later in the middle of the intersection the engine died. No spits, or spudder, just like I turned of the ignition key. I rolled into the gas station at the intersection and parked at the street by the curb. It refuses to start, no spits, the engine just turns over, so the battery is still good. I pulled a plug wire off using myself as the ground, my wife turned the ignition key. Let me tell you, the fire ing still works great.
A friend pulled us home and I started looking for the problem. As far as I can tell it may be the fuel pump relay.
The two fuel pumps are silent whent the key is turned on, and I disconnected on of the fuel injector lines and gas squirted out wiht the key off. I opened the gas cap on the tank to release the pressure and opened the same fuel line as before and the gas just dribbled out. So to me gas is getting to the injector system, but the two fuel pumps are not working.
I looked up everything on this site, to locate the relay, but what I have is different than what is shown here. The pins are different. Can you help me to ID the Fuel Pump Relay?
Does that not say the fuel pump relay has died?

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Old 04-04-2008, 05:10 PM
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Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,211
I think you are on the right track that the fuel pump relay(s) or possible the OVP relay have died. Otherwise it could be the pumps themselves....
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Old 04-04-2008, 07:18 PM
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Join Date: Jun 2004
Location: South Louisiana
Posts: 48
OVP Relay ?

What does the OVP relay do?

I'm having trouble locating the Fuel Pump Relay, The location of the relay in pictures on this site and others shows it next to a relay of sorts with 2 fuses on the top, I pulled that relay but the pins don't match up with the Fuel pump relay shown here and on a search.
There is another relay to the left some that seems to match the pins in pictures of the correct relay, but the location is not the same.

Can you help me to locate the correct relay location?

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Old 04-04-2008, 07:33 PM
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Join Date: Jun 2004
Location: South Louisiana
Posts: 48

I looked and ID'd the OVP relay, I changed it about 3 years ago, but I can't remember why.

I do remember the problem was not the same as it is now. Before the car would start and run, now it's dead.
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Old 04-05-2008, 07:19 PM
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Join Date: Jun 2004
Location: South Louisiana
Posts: 48
Got it running

After searching the information about the Fuel Pump Relay, I decided to go ahead and buy one.
My wife insisted that I had bought something about 3 years ago for the MB, didn't know if it was the problem, but replaced it anyway. So I went looking in the truck for any parts. I always save a spark plug and the box it can in, and an old part in the box of the new part for a little while, just in case.

I looked in the truck, in a small box and found a box, it says Fuel Pump Relay. I did replace it when I had another small problem a few years back. In the box was the original fuel pump relay. I pulled the replacement FPR and reinstalled the original relay and the 420 started right up. I guess the old relay was not defective after all.

The replacement FPR was made by KAE. I don't think I'll buy another KAE brand. The original FPR is 19 years old and still working, the KAE fuel pump relay part only lasted 3 years or so, and let me on the side of the road.

The MB is running great again, thanks for everybodys help!
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Old 04-07-2008, 03:43 PM
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Join Date: Apr 2005
Location: Rockville MD
Posts: 833
There is a way to jumper ther pins on the FPR connector if you get stuck in a bad spot. It will get you running but the fuel pumps will keep spinning until you unplug the jumper. I keep a wire in the glove box with the ends identified with the pin numbers, just in case.
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Old 04-07-2008, 04:23 PM
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Join Date: Sep 2004
Location: DFW / Collin County Texas
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Me too - I still have my specially-shaped paperclip in my ashtray.
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Old 04-08-2008, 07:58 AM
Registered User
Join Date: Jun 2004
Location: South Louisiana
Posts: 48
Tell me more

Please give me more information about how to jumper
do I jumper the FPR pins or put a jumper wire into the pin slots?
Anything. This is the first time ever a vehicle, (MB or not) has left me on the side of the road. Maybe I've just been lucky.

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