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post #1 of (permalink) Old 06-17-2001, 07:22 AM Thread Starter
 
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A Strange EngineProblem

Last Monday morning, after a problem free night of wheeling, Poison Spider Mesa in Moab, I went to start the 5.0, and it wouldnt jump to life. It cranked over fine, I could here the fuel pump whirrring but not fire. This all after a 1000 miles of good performance and hundreds of trouble free engine start ups. This engine usually doesnt take more than a second or 2 on the key to fire it up, in any condition.
I checked the coild and sure enough there was no spark, well naturally I suspected it had to be some of my electrical work. So I started checking everything. But I was getting good voltages at the coil, and I had 12v present at all computer power inputs. I was getting annoyed, and it was time to get out on the trail, but I couldnt find any problem. I told my freinds to hit the trail and I called the local parts stores and went down and picked up a TFI module and a new Stator module, I removed the distributer and replaced both modules, fought with the oil pump drive shaft until I finally accidentally pulled it out of the pump and heard it fall into the oil pan. So I put the distributer back in and tried to fire it, and.... still no spark.
I went back to my manuals from Ford Racing, and just happened to notice I picture of the EEC Power Relay, and could not recall installing one into the socket provided. they had conveniently supplied the Fuel Pump relay and wide open throttle relay, but I still couldnt recall seeing the EEC power relay, so I pulled out the computer from behind the glove box, and low and behold,..."no relay".
I had never been able to get the fuel pump relay to work propperly from the start so I had rigged, my own pump relay off of the ignition switch, and had not thought anymore about it.
So I went back to town and purchased a 12 dollar EEC power relay, but didnt think it would make any difference since I have been running without it for months, plugged it in and whaaaala the engine fires right up(although i shut it right off due to no oil pressure). I also picked up a oil pump shaft at the parts store,, so I dropped the pan installed the new shaft, applied a shload of silicone to the oil pan gasket and main seals, bolted it back up, filled it with oil and went wheelin. It has ran great since, and the Ford Harness fuel pump relay now works(which is nice because it shuts off the pump after pressurizing if the engine isnt started right away).
How could it have ran for so long if the EEC power relay is neccessary for the engine to run?
Why did it not start after running so long, if the EEC power relay, is not neccessary for the engine to run?
I wonder if it recieved some signal from the computer that required a reset signal that could not be generated without the relay? Very confusing, the techs at Ford dont think it should have ran without the relay. No other changes in engine performance were observed.
Anyone care to try to hypothysize on this electrical conundrum?

Jeff
89 YJ
Wow, you can get a nice tan on your arms, from welding with no shirt on.
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post #2 of (permalink) Old 06-17-2001, 09:39 AM
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Re: A Strange EngineProblem

It's been a while since I screwed with a Ford. I never could tell the difference between the EEC power relay and the fuel pump relay. I think one of them has a brown color code, and the other has a green color code. What if you got the relays mixed up? Another possibility would be the way you wired up the original fuel pump relay. Could you have feed power to the EEC relay through the fuel pump relay? This could be a possibility.

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post #3 of (permalink) Old 06-17-2001, 09:55 AM Thread Starter
 
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Re: A Strange EngineProblem

No the EEC Power elay is a completely different 5 pin configuration and is located right by the EEC IV Computer.
You are thinking of the Fuel pump Relay and the Wide Open throttle Cut out relay, they are identical in shape and located right next to each other close to the mass air meter. I dont have any actual shop manuals for the electrical, just a very comprehensive install guide from Ford Racing. The Chiltons and Haynes manuals dont tell you diddly squat.
So Im not sure axcactly what the the EEC Power relay controls, but, on Monday morning I know it was controling the output voltage from the coil(I think, through the TFI module). But again, I keep asking myself, why did it not have any impact on engine performance up to that time?

Jeff
89 YJ
Wow, you can get a nice tan on your arms, from welding with no shirt on.
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post #4 of (permalink) Old 06-17-2001, 10:01 AM Thread Starter
 
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Re: A Strange EngineProblem

As far as how I wired the fuel pump relay, I just abandoned and shrink wrapped the output from the Ford Fuel pump relay(the output would normaly just run to the fuel pump positive), and ran a completely redundant relay using the start/run position on the ignition as the trigger signal. Since I already have everything hooked to the pump, I simply ran the Ford fuel pump output to the trigger signal wire on my already exhisting fuel relay, and abandoned the trigger wire from the ignition.

Jeff
89 YJ
Wow, you can get a nice tan on your arms, from welding with no shirt on.
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post #5 of (permalink) Old 06-17-2001, 10:27 AM
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Re: A Strange EngineProblem

At least you are up and running now, and that is good! I'm in the middle of a mess. My CJ-7 is running good with a home made harness from a '95 XJ on a 4.0l. I built a 4.7 stroker, and planned on wiring it up to a '98 ZJ harness I built, but then I came across 5.9 Magnum. So far I have $2400 in the Magnum, and had to completely rewire and built a new dash that uses a '98 ZJ instrument cluster.

Last week we signed a contract on a new house with 40 acres in the mountains near Salida Co. My new driveway is the entrance to Waugh Mt. pass. I have to start sellling off many of my projects for the down payment. Anybody need a 4.7 stroker wired and ready to go? How about a 3k mile NV-4500? Two newly built AX-15's? A good Dana 60 high pinion housing?

The Saab convertable is going. Yesterday, while wheelin in Hacket's gulch, I asked the little woman if it would be ok to sell off the CJ and she came unglued on me! DON'T EVER SELL JEEP! What a great 'lil woman.



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post #6 of (permalink) Old 06-17-2001, 10:32 AM Thread Starter
 
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Re: A Strange EngineProblem

Hmmmm, Ive been thinking about building a high pinion 60 for the rear, but thought I would wait untill winter. What excactly does the D60 housing consist of, how much you want for it. I shouldnt even ask, I dont have the time for another project, but what can I do,..Im weak.

Jeff
89 YJ
Wow, you can get a nice tan on your arms, from welding with no shirt on.
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post #7 of (permalink) Old 06-17-2001, 10:59 AM
 
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Re: A Strange EngineProblem

I had a probem with my new MPI setup for the first month ...
Dang thing would just not fire up every so often and would leave me stranded.
I finally figgered out that I could't hear the fuel pump 'bump up' on these occasions and realized the ignition/fuel pump relay was unreliable.
After I swapped it out it fires up every time, all the time ... until I got back from Moab last week...
I'd come home and gave the 'baby' a good top to bottom power wash and drove it home. The next morning the battery was almost dead and listening carefully I could hear the fuel pump softly 'bumping'.
Yep, you guess it. The same dang relay had taken in some water and had shorted out.
Moral ... keep and extra relay handy ... you can't go home without one [img]/wwwthreads_images/icons/smile.gif[/img]!

P.S.
I'm told these relays come in inconsistant qualities.
The one I just bought another spare from CarQuest yesterday, was 20 bucks and it was a 'no name' generic !
I'm gonna look for a top of line Bosch or Hella brand ... and water proof if I can get one.
Hummm, think I saw one like that somewhere ... Painless Wiring Catalog ? ... I'll have to check ...

JAF
http://www.monsterslayer.com/jeep
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