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  #1  
Old December 8th, 2003, 17:52
secutores secutores is offline
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Question Fuel Pump Relay Haywire?

Hey all, I'm new here, but I read through like 50 pages to be sure I wasnt posting some rediculous question. Here it goes:

My '89 2.5L cherokee didn't want to start the other day and I'm trying to figure out the problem, I made sure it had fuel in the tank, and spark and a full battery, but I cant here the pump prime when i turn the key. I got it running but it kept cutting out every 20 seconds or so and then it wouldnt start at all. I heard a rapid ticking from the fuel pump relay, (another post said it was the second one back on the passenger side fender) and the shift light on the dash was flashing in time with it. I tested the plug for the relay and it has one constant 12 volt and one switched 12 volt, and I replace the relay. Still no dice, its still clicking and I dont know what to do next.

Does anyone have any suggestions about what I should check next? Also, can anyone tell me what the first relay controls, because it was also ticking, and can anyone describe what the ballast resistor looks like so i can examine that too?

Thanks, Colin Clark
(great board by the way)
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  #2  
Old December 8th, 2003, 18:53
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Lou Lou is offline
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Re: Fuel Pump Relay Haywire?

I'm not exactly familiar with the 89 but I'll give you a couple of things(relative to my 91).

The other relay is(?) the ASD(automatic shut-down) -- don't ask me what that does.

On my '91 there is a common power feed from the ECU to both of these relays. The ECU also drive these two. You may have the RENIX...so I don't if that still applies.

The ballast resistor is(?) mounted on the driver's fender wall. It is a whitish ceramic block(.5x.5x3").

Relay chatter can be caused by low voltage, or a bad connection to the relay coil.

Try running it, and then go around wiggling the harnesses

Also to note .. the fuel pump is only primed for a few seconds. I just learned that recently ..
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Old December 8th, 2003, 21:54
secutores secutores is offline
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Re: Fuel Pump Relay Haywire?

Thanks Lou!

Well I guess I need to know if I should replace the other (ASD?) relay too... or if the harness is hosed, replace that...

Does anyone know what else could make the relay's chatter? The battery was putting 12.2 volts through, which I know is kinda low, but it seems like it should be adquate.

Also, the fuel pump isnt priming at all.. Back in the days of carberators you could just pop the fuel line and see if some squirts out, but I dont know if thats a good idea with a 40 psi fuel pump. Anyone want to tell me thats a good or bad idea?

I just dont know what to check next.

Thanks Group!
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  #4  
Old December 8th, 2003, 22:22
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Matthew Currie Matthew Currie is offline
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Re: Fuel Pump Relay Haywire?

It might be a good idea to check the ignition switch.
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  #5  
Old December 9th, 2003, 02:30
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churky89 churky89 is offline
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Re: Fuel Pump Relay Haywire?

Just tossin in my .02.....Change the fuel filter?My 89' was actin kindasorta like that@a week ago.I was thinkin it was the fuel pump,but changed the fuel
filter and that cured it.
Of course,this post means that the fuel pump will now go out LOL!!!
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  #6  
Old December 9th, 2003, 05:46
89xj 89xj is offline
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Re: Fuel Pump Relay Haywire?

also check the ballast resistor for cracks and resistance. should be 1.1 ohms. its located on the drivers side fender wall. its a white ceramic resistor with 2 leads.
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  #7  
Old December 9th, 2003, 08:09
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Re: Fuel Pump Relay Haywire?

The other day my new old 84 2.5L did something like that. it was either a fuse in the fuse block or a loose wire. I wiggled all the fuses and pressed the wires on the back into the block. She fired right up. Check the easy stuff first. If it's not priming its most likely not the filter. But I would change it to rule it out.
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  #8  
Old August 7th, 2009, 20:07
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GoSlowGetStuck GoSlowGetStuck is offline
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Re: Fuel Pump Relay Haywire?

What's worse? Posting a new thread and being told to search, or resurrecting a 6 year old thread from the dead? I dunno, but I'm doing it anyway.

Just installed Jon Kelly's (5-90) wiring kit on my 89 XJ since my ground/starter wires melted due to a short circuit. I had taped up those wires and the thing still ran, so I don't think that screwed anything up. Although coincidental, I don't think the new wires have anything to do with the problem. I have pretty good electrical knowledge and trust me, things are wired up correctly. I replaced the B- to engine block, B+ to starter, and B+ to starter relay wires (or ignition module, or distribution block, or whatever the damn thing is called that connects directly to the battery). I replaced the existing alternator to starter relay fusible link with a direct, ANL-fused wire from the alternator to B+.

My symptoms are the rapidly clicking fuel pump relay (second relay from front), and the fuel pump will not turn on, and won't prime, and the vehicle will turn over but won't start. I have 12.6 volts at relay pin 30 (constantly), and 12.6 volts at relay pin 86 (switched, on with key). Swapped the fuel pump relay with the other relays there and nothing changes.

It's hard to believe my ECU is fried and it can't ground out the fuel pump relay to energize the coil. Checked the ballast resistor (can't even find the damn thing on the wiring diagram, but oh well) and it reads 1.8ohms, which IMO is close enough. Kinda lost here... my XJ is just a trail toy but I kinda want to go wheeling tomorrow

In the meantime I'm just going to wiggle wires and hope that's the problem, I mean the thing's only 20 years old...
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  #9  
Old August 7th, 2009, 20:40
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GoSlowGetStuck GoSlowGetStuck is offline
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Re: Fuel Pump Relay Haywire?

OK... as previously mentioned, pin 30 has a constant +12V from the battery. If I remove the relay and short pin 30 to pin 87 (the other side of the relay *contact*, that goes to the fuel pump) the pump turns on and stays on as long as I'm connecting them. Also, if I tap into pin 85 (ground lead of the coil which goes to the ECU), turn the key to on (so that the other side of the coil, pin 86, receives power), and then connect 85 to battery ground, the pump runs as long as I do that. As soon as I stop grounding out pin 85, the ECU takes over and the relay resumes the rapid clicking, but then eventually stops.

I've read that after the key goes to on, the fuel pump runs for 4 seconds (or however long it is). Is this a fixed number or is it based on some other sensor, for instance the ECU turns the pump on long enough to build fuel pressure for starting, then turns off? If so, could this sensor (I have no idea what/where it would be) be causing a problem? I have to imagine the problem is in the vicinity of the new wiring...

If I can't get this working properly... how bad of an idea is it to either run some decent-sized wire and put the fuel pump on a switch directly, or else tap into the pin 85 of the relay and run that to a switch which grounds it so the pump can run. Ideally I'll get this fixed "right" soon but given that it's a trail-only rig, I really am just concerned about how to get up and running tomorrow.
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  #10  
Old August 7th, 2009, 20:59
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Re: Fuel Pump Relay Haywire?

The fuel pump is supposed to run whenever the key is in the start positon and 4 seconds after it is released to run position. When the ECU gets the signal from the crank positon sensor that the motor is turning, it continues the signal for the fuel pump. Is the ECU ground good?
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  #11  
Old August 7th, 2009, 21:09
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GoSlowGetStuck GoSlowGetStuck is offline
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Re: Fuel Pump Relay Haywire?

Quote:
Originally Posted by winterbeater View Post
Is the ECU ground good?
... damn! I owe you a beer, winterbeater!

As soon as I read your post I remembered the ground wires coming out of a wiring harness that go to the ground stud on the engine block. Of course I grounded the battery to the block, but those wires were just hanging there. Hooked them up and turned the key, fuel pump primed and it turned right over (well after 10 seconds or so, it is a Renix...)

I get to go wheeling tomorrow!!! Thanks again winterbeater for jogging my failing memory!

I guess this probably doesn't help the OP, but to anyone else who finds this thread... check your grounds...
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  #12  
Old September 17th, 2009, 00:31
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AJTorris AJTorris is offline
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Re: Fuel Pump Relay Haywire?

sorry for bringing up an old thread from the grave yard but i just wanted to chime in and say i had the same issue just now and looked it up and found this thread and BINGO!!! It was the ground wires
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