Help interpretting codes
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Laughing Gas
Joined: Aug 2010
Posts: 982
Likes: 49
From: Northern Kentucky
Help interpretting codes
I have an '89 F250 that I just got cheap; 302 EFI 5 speed. Having some intermittent run problems and had the codes pulled at AutoZone. The code we got (KOEO) was 87 which says "primary fuel pump or fuel pump relay circuit failure". I'm an old guy and have not worked on FI vehicles before. Carbs I understand but EFI not so much. My questions are: a) is the Primary fuel pump the high pressure pump on the frame rail?
b) if you have a fuel pump failure, wouldn't the truck just quit running?
c) how do you check the fuel pump relay circuit? I have a Haynes manual but the chart and diagrams for fuel delivery area might as well be written in Russian.
The problem I was having was occasional cutting out under hard acceleration, almost sounded like cross-firing but the plugs, cap, rotor and wires are new, and wires are properly routed and spaced.
Any help would be appreciated.
Whisler
b) if you have a fuel pump failure, wouldn't the truck just quit running?
c) how do you check the fuel pump relay circuit? I have a Haynes manual but the chart and diagrams for fuel delivery area might as well be written in Russian.
The problem I was having was occasional cutting out under hard acceleration, almost sounded like cross-firing but the plugs, cap, rotor and wires are new, and wires are properly routed and spaced.
Any help would be appreciated.
Whisler
Senior User
Joined: Apr 2010
Posts: 324
Likes: 1
From: San Tan Valley, AZ
It sounds to me.... that if it's cutting out under hard load, it's not getting enough fuel when it needs it. ie the high pressure pump. But for some reason I thought these truck had only one pump per tank?!? Has the truck had the check valve recall done to it? do you have two tanks?
I'd start with a wire check. Then I'd get a fuel pressure gauge, and run the truck until it cuts out to see what the pressure reads.
One more thing.... think about changing the filter?
I'd start with a wire check. Then I'd get a fuel pressure gauge, and run the truck until it cuts out to see what the pressure reads.
One more thing.... think about changing the filter?
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
'90 was when they switched to a simpler fuel system with just high pressure pumps in the tanks, so this '89 has the old system with seperate high and low pressure pumps and a frame mounted switching valve. You need a fuel pressure gauge to monitor what happens when the truck dies, code 87 is often a phantom code so I wouldn't put much stock in it unless you can verify that the system is loosing pressure, it's more likely your problem is electrical and related to the ignition system.
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Laughing Gas
Joined: Aug 2010
Posts: 982
Likes: 49
From: Northern Kentucky
Thanks for the replies! The truck does have dual tanks with the pump in each tank and a pump on the side rail. The truck never really dies but just refuses to accelerate properly and seems like it is cross-firing or missing. I'll see about checking fuel pressure, and check the spark plug wires again although I have done this several times. I saw a diagram posted for a very specific wiring route to avoid inductive cross-firing on thes engines. I'll see if i can find it again and utilize it. By the way this truck has platinum Autolite plugs, which I have read some criticism of. what is the knock on platinum plugs?
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