87 YJ w/360 amc swap can't keep it runnin

[Indiana XJ]

aight heres the problem got a 87 YJ with a t-999 tranny an a 75 amc 360 swapped in did the swap bout a year ago an friday i started it up an it ran fine just like normal till the end of the driveway then it died an wouldnt start again let it sit for awhile an it started back up an ran for bout 15 seconds then it died again an its been doin the same thing since then i cnat get it to run for longer than 15-20 seconds i replaced the coil, plugs,wires an solenoid an it didnt help ive got juice runnin to everything an everything seems to be workin fine but i just cant keep it runnin the carb is an edelbrock 650 4 barrel an its workin fine to i tried playin with the adjustments but nothin seemed to matter i had a problem before when i did the swap i had to run an 86 wagoneer distributer to make all of the wirein match up an the pickup coil went bad on it but near as i can tell it seems to be workin correctly anybody out there have any ideas?????? HELP!!!

[Rattlecan]

Got enough fuel coming from the pump? What pump did you use to provide flow to the 650?

[fullygruntled]

Sounds like a bad Duraspark ECM (assuming you have one)

If you swapped over the entire Prestolite ignition from the '75, replace it all immediately with a Duraspark TFI setup (search here or google) or HEI ignition (again, search here or google). The Prestolite will do stupid shit like that essentially at random.

[NVCJ]

Sounds like fuel to me:D

[Indiana XJ]

okay i worked on it some more this evenin the pump is the stock mechanical one (replaced it when we did the swap so its less than two years old) its workin just like it should, no i do not have the prestolite inginition if thats what u mean by the ford style brainboxes an all that crap i swapped in a distrubuter from an 86 wagoneer an it does away with the boxes an uses the yj 4.2 wiring that was in it (took some time but it works)

[fullygruntled]

fairly simple and obvious, but have you checked the fuel filter yet?

[Rattlecan]

^^^ Agreed

Very much sounds like fuel a fuel delivery problem.

Fuel pump, vac. leak, fawk even a fuel filter clog.

If it runs for a while and dies you have spark, and all of the sensors (well.... the few you have left) seem to be doing their job... If it is running OK then your timing is good enough... Yup gotta be fuel.

[72fj40]

Is it flooding out or fuel starved? Are you running the stk style AMC fuel filter w/the return line port on it? From past experiences, it needs to be hooked up. If the return line is blocked off at the filter, or if a filter w/only an in and out port was installed, it will eventually cause the carb to load up. You probably could install a pressure regulator too.

[Indiana XJ]

okay first off the fuel filter is new an it had no effect, the fuel return line is hooked up an workin, an after screwin with it some more ive come across this an now im Very confused here it goes tell me if im crazy or if my jeep is possesed but after it starts an runs for the 20 or so seconds before it dies then when u try to start it again there is absolutely 0,none,nada,nothin for spark on the plugs absoulutley no spark at all on any of em now this is with new plugs,wires,cap,rotor an it ran fine before an after i changed em an it will still start an run but only 15-20 seconds or so then it dies an has no spark (i found out this evenin) an then let it sit for awhile an it will fire right back up for another 15-20 seconds so im headin into town now to get a new coil an try that also could it be possible that the 4.2 harness is trying to put to much power through the 360 coil an burnin it up?? ive read somewhere that u have to use a resistor between the hot wire into the coil an the coil itself is this true?

[fullygruntled]

I return to my previous diagnosis of a bad ECM. I'd wager fifteen cents on it.

[Indiana XJ]

okay ecm=engine control module so that is the box up under the dash on the passenger side right? i always heard it called the iginition control module (same thing or am i bassackwards?) if so is there a way to test it short of shellin out the $ for a new one?

[CJ5inNE]

okay i worked on it some more this evenin the pump is the stock mechanical one (replaced it when we did the swap so its less than two years old) its workin just like it should, no i do not have the prestolite inginition if thats what u mean by the ford style brainboxes an all that crap i swapped in a distrubuter from an 86 wagoneer an it does away with the boxes an uses the yj 4.2 wiring that was in it (took some time but it works)

This is where Im lost. If your using stock 4.2L wirring, then you should have a duraspark (not to be confused with prestolite) module somewhere. A little grey 4x4" box that may very well say duraspark, or motorcraft on it. an 86 wagoneer would have used the same module. But a regular wagoneer that year would have had a GM 2.8L v6 wouldn't it? So what are you using for an ignition there?

In any event, if somewhere in that mix you have a duraspark module, then it sounds like its going bad. They have a thermal overload breaker inside, that will trip when it gets too hot, and shut down. They do tend to be problematic. I actually had two bolted to my fender so that if and when it took a crap on me, I could just plug the other in and be on my way.

Ohh, and the ECU mounted behind the dash is not working anyway if you've put in a 360. That was mainly for emissions related hardware, and the carter BBD carb. So Im going to say thats not your problem.

[rustywagoneersdotcom]

duraspark module

peace
Dave

[Indiana XJ]

okay ur right CJ5inNE its not the ecm i got lost in the terminology a lil last night an its actually my dads jeep he did most of the wirin on it i handled the mechanical part the ecm is NOT hooked up at all he said he did away with that on the swap, the distributor is a NAPA part that we cross referenced an it is off of according to them an 86 wagoneer with a 360 v8 anyway it works so why mess with that part. were in plantin season full swing here right now on the farm so its kinda tough to get time to work on stuff when it early when u start an late when u finish so im hopefully ill have sun afternoon off im gonna try a resistor, put the new coil on it, an then check the duraspark thing ur talkin bout exactly where should it be located on an 87 yj sorry not the sharpest tool in the shed when it comes to electrical

[YME]

There should be three wires coming from the base of the dizzy- Purple, orange, and black IIRC. Trace those wires around until you get to a box. That's your Duraspark module. Don't change out the coil or any thing else until you find that box and swap it out.

[Indiana XJ]

okay so purple orange an black i can handle that im assumin they are gonna be on a plug or snap connector of some kind? am i lookin to head up towards the firewall/under the dash or should it be a fender mount job? an u say not to swap out the coil yet any particular reason since i already have a new one ready to put on?

[Indiana XJ]

ITS ALIVE!!!!!! thanks a bunch everybody who helped me out on this one the duraspark module was the culprit an now that its replaced she runs like new again thanks again for all the help everbody thats why i love this forum. also i got a quick question is there a way to bypass it an not use it or run something a lil more reliable?

[rustywagoneersdotcom]

how many miles on the jeep? 2nd engine... and this is the first one it needed... hard to beat.. now, some of the dimestore ones might fail early, but an original, or good quality duraspark may not be sexy, but they are stout.

peace
Dave

[Indiana XJ]

it had 86,000 when we pulled the 4.2 out an put the 360 in now its pushin close to 90,000 an i buy all my stuff from napa even if they are a lil more sometimes there stuff seems to last longer oh an it was the factory module still in it it didnt have duraspark or motocraft on it it had AMC written on it

[rustywagoneersdotcom]

well, stuff like that it pays to keep a spare, but there probably isn't much out there that would be more reliable...

peace
Dave

[fullygruntled]

Called it on post #3 :D

Anyway, it's not a terrible unit, and spares can be had on the cheap. Many AMC's and Fords of that era used the same box, and most junkyard units still run just fine.

If you're still itching to ditch it, try an MSD 6 control module.

[Indiana XJ]

dang it im back again it ran great for bout 3 days an now its back to crap again itll run fine for a mile or two just like it should then it just falls flat on its face cuttin out an generally runnin like crap so ive been workin on it the last few nights an heres what ive come up with so far (new coil,swapped plug wires/made no difference thought it was worth a try though,new plugs again,new fuel filter,replaced all the fuel lines,replaced all the vacum lines with new, checked an can find no vacum leaks anywhere, had the carb rebuilt again its perfect put it on an old truck to check it out an it runs like a top, new fuel pump/no change,ran a bottle of sea foam through the tank, an new icm still its runnin like crap an im outta ideas hate to beat a dead horse but any ideas on this one?

[fullygruntled]

What sort of charge are you getting from the alternator? A chronic overcharging condition can kill control modules fairly quick.

[Indiana XJ]

gauge is readin around 13 volts

[Indiana XJ]

ive found the culprit!!!! here is what ive discovered over the last month of bein severly fawkin pissed at this thing which aint even mine an i dont get to wheel!!!!! the problem turned out to be the coil all along when i got another new one for it i ordered one for the 4.2 iginition which its still using instead of for the 75 360 like what has been on it an did away with the resistor an all i can figure is that the coil from the 360 was not puttin out enough an then when paired with the resistor was not allowin enough juice to get through an keep it firin an also had to collapsed lifters an a couple broken pushrods but now shes runnin like a top if only i can get that dang edelbrock lined out thanks again for all the help guys ur life savers