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Fuel Pump Circuit 1995 1996 5.8

S

salemsled

New member
I posted this in other mfgs, but my engine is the same as an OMC 5.8L MFI from 1995-96
Perhaps somebody here will be able to shed some light on the subject.:rolleyes:

I have a 2000 Thunderjet Alexis Classic that has a Redline marine engine. The engine is a Ford 5.8L H.O. MFI Using EEC-IV ignition with high and low pressure fuel pumps.

I have been experiencing the following problem with the fuel pump circuit. The 20amp circuit breaker trips when I go to start engine. This breaker does not trip every time I go to start, but at least 75% of the start-up attempts. Circuit breaker trips mostly on initial startup and after running for a while(1 hour or more) and shutting the engine off and then trying to restart.

I have been through the wiring harness double checking for ground and wiring problems(none found). I have also cleaned and double checked Ignition circuit and replaced relays and all appear and test good. Batteries are fully charged.

My concern is that I have an electric fuel pump /pumps that may be on the verge of complete failure due to ethanol related fuel problems. (water in fuel). The fuel system does have a fuel water separator that I change every year but can this e-fuel be such a problem that more frequent service is required.

My hope is that you guys on this forum with more engine experience than I can help answer the following question,
Can this water intrusion cause damage to a fuel pump that would require more amps to operate pump thus tripping the 20 amp circuit. (Intermittent failure):confused:
I have connected code reader to engine and received code 96 in ECA memory. Fuel pump circuit open-BAT-to-relay

Is my theory just completely wacked or am I on the right track. I want to know if my next step is to replace the fuel pumps.
Thanks in advance for any help
 
Re: Fuel Pump Circuit

You checked the fuel pickup tube in the tank to see if it's clogged ? Vent is clear ? The anti-syphin valve is clear.
 
Re: Fuel Pump Circuit

If you can run the engine for an hour then clearly the issue is not related to the fuel pumps going bad. Have you tried replacing the 20 amp breaker with a known-good one? If the breaker is the faulty part it will save you about $500 in fuel pumps. If it's one of those good for nothing red push button breakers, swap it for an actual honest to goodness Carlingswitch magnetic trip breaker or even a fuse.

That's where I would start.
 
Re: Fuel Pump Circuit

o2batsea

That was the first place I went to when this started. I replaced the breaker and still have same problem. (but not as fequent)

My thought is once the fuel pump is running its not drawing as many amps, but when the fuel pump initially starts up it is requiring a few more amps then the circuit is rated for and it trips the breaker.
 
Re: Fuel Pump Circuit

o2batsea

thanks for taking the time to help out with this problem, I will keep you posted as to what happens.
 
Re: Fuel Pump Circuit

I have both the high and low pressure pumps that I bought thinking I was gonna convert to EFI, but that never happened. They are both brand new unused and I'm willing to part with them for a very good price. If you think that you need to replace the pumps I'd like to help you out. Not looking to make any money, just what I paid. Good to have as spares anyway. I can get pics if you like this weekend. I even got some Bosch plug pigtails so I could hook them up to my Ford EFI computer.
 
Re: Fuel Pump Circuit

yep replace everything and anything, without trying the basics first.

But the pumps will go eventually never hurts to have spares.
 
Re: Fuel Pump Circuit

boatin_bob,
Thanks for the help. I have run continuity tests on fuel pump and ignition circuit. I have replaced relays and circuit breakers.
I feel pretty confident that the wiring tests have shown the electrical system is good.

The theory of a fuel pump high amp draw is the last explanation I can come up with to explain the circuit breaker constantly tripping on startup.
Thanks for your input and I will keep you posted as to what happens after I swap the pumps.:confused:

Before I change these pumps...
I will jumper accross circuit breaker and check amperage draw at start-up just to confirm that the pumps are drawing to many amps for just a split second at start.
The whole reason I posted here was to get some input on the idea about the pumps being worn out and drawing to much power.
 
Re: Fuel Pump Circuit

I think if the pump is worn out (brushes) it will simply not do anything...won't draw big amps, nothin, just sit there like a lump. If there is an intermittent short inside the pump, then it would pop the breaker.

Since the pump is a sealed unit you'll have to exchange it with a known-good pump to find out. So in any case there is some wrenching in your future.
 
Re: Fuel Pump Circuit

Wow!! Sounds similar to what I'm dealing with right now. I have a '96 sprint that has had a '99 351 Red line put in it. Ran like a champ never had any problems for 4 years. Did not winterize:confused:. Got water in the fuel system and hasn't ran right since. Both fuel pumps were shot. The hi press pump would get hot and the others bearing got messed up so the impeller was rubbing on the housing. Replaced both and now get pressure to the fuel rail then lose it as if it was bleeding off. I have the rail/injectors off on one side and have cranked it over with nothing coming out. I may need a fuel system schematic. Any Ideas?:D
 
Re: Fuel Pump Circuit

Another bit i forgot to add was that i ran the boat this spring and it only ran on four cylinders on the even side. Are there any red line manuals out there or any other references that i could use?
 
Re: Fuel Pump Circuit

QDOG001
I have not been able to find a Redline Manual. I use a Seloc #3404 and Clymer# B739 for OMC. I do have a download for Volvo Penta EFI troubleshooting guide for Ford engines. PM me and I will send it to you.
Did you ever have circuit breaker fail on fuel pumps?
 
Re: Fuel Pump Circuit

Checked wiring and connections again on fuel pumps, breaker and relay.
All look and test fine.
Swapped out the fuel pumps and took the boat out Saturday.
Boat ran perfect, no hesitations and started on first attempt each and every time after shutting the engine off.
Boat ran for 3-4 hours up and down the river.

Pumps were the culprit, they were 10 years old and they were just getting tired.

Thanks everybody for all the help.:)
 
Re: Fuel Pump Circuit

salemsled said:
I posted this in other mfgs, but my engine is the same as an OMC 5.8L MFI from 1995-96
Perhaps somebody here will be able to shed some light on the subject.:rolleyes:

I have a 2000 Thunderjet Alexis Classic that has a Redline marine engine. The engine is a Ford 5.8L H.O. MFI Using EEC-IV ignition with high and low pressure fuel pumps.

I have been experiencing the following problem with the fuel pump circuit. The 20amp circuit breaker trips when I go to start engine. This breaker does not trip every time I go to start, but at least 75% of the start-up attempts. Circuit breaker trips mostly on initial startup and after running for a while(1 hour or more) and shutting the engine off and then trying to restart.

I have been through the wiring harness double checking for ground and wiring problems(none found). I have also cleaned and double checked Ignition circuit and replaced relays and all appear and test good. Batteries are fully charged.

My concern is that I have an electric fuel pump /pumps that may be on the verge of complete failure due to ethanol related fuel problems. (water in fuel). The fuel system does have a fuel water separator that I change every year but can this e-fuel be such a problem that more frequent service is required.

My hope is that you guys on this forum with more engine experience than I can help answer the following question,
Can this water intrusion cause damage to a fuel pump that would require more amps to operate pump thus tripping the 20 amp circuit. (Intermittent failure):confused:
I have connected code reader to engine and received code 96 in ECA memory. Fuel pump circuit open-BAT-to-relay

Is my theory just completely wacked or am I on the right track. I want to know if my next step is to replace the fuel pumps.
Thanks in advance for any help
Click to expand...

I have a Red Line 351- recently discovered (the hard way) that there is a safety diode in the purple wire to the fuel pump. Something to protect for sudden oil pressure loss. It is a mystery why my diode failed.
 
Re: Fuel Pump Circuit

Hey Blackbird,

Thanks for the heads up about the Diode on the Purlpe lead, I saw it in the wiring diagram and I new it was there.
I did freak out a little bit when this first started because I immediately thought that the Diode could be giving me some greif and I didn't have a clue were to get a replacement.:confused:

Thanks again
 
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