Gen 2 Mark VIII will not start after motor swap

kustomizingkid said:
I don't believe for 1 second that the car is flooding... efi cars don't flood...
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I have seen it twice and both were related to a damaged PCM (one Chev Van, TBI, had been ran in water and it got in the PCM, the other was a mid 90's F150, 4.9, alt regulator went out and pretty much fried PCM)

Back to the OP...

An aftermarket Jet Performance chip was removed from the computer

Try swapping the PCM another Mark 8...maybe damaged the PCM by static discharge but not enough to kill it completely?
 
Interesting...I think the mechanic was gonna get a hold of a spare PCM today anyway and throw that in there for good measure. I'll update on the results of that.
 
there will be no vacuum at the regulator until the vehicle is running, default pressure is set by the regulator and the ECM changes this via vacuum from the engine.
 
Tiltedhalo said:
there will be no vacuum at the regulator until the vehicle is running, default pressure is set by the regulator and the ECM changes this via vacuum from the engine.
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The PCM doesn't control the fuel pressure. It is a mechanical regulator that if supplied normal engine vacuum will produce a lower fuel pressure. If that vacuum is low or not there, then the fuel rail gets maximum fuel pressure. The PCM can control voltage to the pump. During start or high engine demand, the pump gets battery voltage, all other times it gets a reduced voltage. This is done to reduce noise and to prolong pump life.
 
XLRVIII said:
yea it's soundling like a PCM issue..
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Alright, so I'm gonna start down the road of throwing parts at it until something works. No local spare computers around like I thought, so the cloest and cheapest one I found is 50 miles away for $85 that I can pick up tomorrow. Now I want to make sure we are all talking about the same computer module. The likely culprit would be the computer module under the dash on the driver's side right? The one that has a service port on it right? Mine had an aftermarket chip plugged into it (since removed) and has a model number F8LF12A650EA which I understand is specific to the LSC model, which I have. I don't want to be chasing a goose all over the countryside for nothing! Will this introduce a problem with my programmed ignition keys?

By the way, thanks so very much to all who have chimed in and offered advise. I have learned a bunch and have kept my sanity through the process by being able to find answers. You are very much appreciated. Keep it up because it's not running yet!
 
Key programming is stored in the SCIL, no issues there...and yes you are talking about the PCM under the driver's side dash
 
Can't get a computer replacement until Tuesday. Arrrgh! I originally started this journey on Memorial Day weekend. Perhaps it will be finished by Labor Day!
 
Update after computer swap

Well guys, I got hold of a used computer with matching part numbers from an identical Mark VIII and put it in. All the same problems described above persist. :( It will almost try to sputter to life with WOT and run for three or four seconds but then it quickly dies as it floods. I took the plugs out to check compression again and they were all soaking wet. Compression was good by the way with all cylinders hovering around 150 or better. We've had a few knowledgeable guys come and take a look at it with fresh eyes and everyone just walks away dumbfounded. Any more ideas?

If you read earlier in this thread, I raised a few questions about vacuum. I'm not sure that there isn't some problem related to the apparent lack of vacuum being produced while cranking. How many critical systems have to be functioning during startup that need proper vacuum? Just a thought.
 
OK this is going to be a wild ass out in left field guess...maybe it's pulling excess fuel or fuel vapor from the EVAP system (solenoid stuck open?). With this excess vapor plus the rich start up mixture, that may be the reason it's flooding. When you disable the fuel pump, then the mixture evens out enough for it to run until the engine is trying to run on vapors alone and then dies. The way to check this is to disconnect the hose on the intake that the EVAP is on. It's attatched to the black hard line..look where the a/c evap core connects to the accumulator. It's a hard line about 3/8". follow it until it changes to a regular rubber hose. Try pinching it off or plugging this hose and see if it will run. I know it's waaaaay out there, but I have seen stranger.
 
Hmmm. Certainly worth a try. I'll check it out and post back.
 
rayner601 said:
I know it's waaaaay out there, but I have seen stranger.
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that's a fairly sound idea.. and at this point.. the solution is either going to be something stupid simple or WAY WAY out there.
 
rayner601 said:
OK this is going to be a wild ass out in left field guess...maybe it's pulling excess fuel or fuel vapor from the EVAP system (solenoid stuck open?). With this excess vapor plus the rich start up mixture, that may be the reason it's flooding. When you disable the fuel pump, then the mixture evens out enough for it to run until the engine is trying to run on vapors alone and then dies. The way to check this is to disconnect the hose on the intake that the EVAP is on. It's attatched to the black hard line..look where the a/c evap core connects to the accumulator. It's a hard line about 3/8". follow it until it changes to a regular rubber hose. Try pinching it off or plugging this hose and see if it will run. I know it's waaaaay out there, but I have seen stranger.
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I pinched off the rubber line as suggested...no improvements.
 
My turn for a wild assed guess.

VCRM..

On tiffs 94 it wouldn't fire the injectors, the culprit was the VCRM.

hanging the injectors wide open? might be also a VCRM issue.
(located on the bracket that holds the air ride pump)
large aluminum finned box with a very large electrical connector, the connector has a bolt holding it into the VCRM
 
Another vote for VCRM... it controls the low speed fuel delivery...
 
Tip: when you talk to the folks at the junkyard..
dont tell them how important this box is.

Tell them its a relay control box that controls the electric fan and your mechanic sent you after one.

DO NOT TELL THEM the engine wont run without it, that doubles the price.

last VCRM I bought was 20.00
 
Going out on another limb here, take a jumper cable and connect to the negative battery post and attatch the other end on the engine. Take another one and connect from the negative battery post and the other end connect to the ECM case. Got the idea from here..link I know it's a Mustang site, but for the most part fuel injection works the same.
 
Ok, we may be on to something. Just mentioned all this to my mechanic and he told me there was someone looking at it last week that noticed that the fan wasn't working. Perhaps we've got a bad part? I called the only yard around with a mark viii and they're gonna check to see if they have one. I'll post back with results. Hope we're going the right direction finally!
 
renkenj said:
Ok, we may be on to something. Just mentioned all this to my mechanic and he told me there was someone looking at it last week that noticed that the fan wasn't working. Perhaps we've got a bad part? I called the only yard around with a mark viii and they're gonna check to see if they have one. I'll post back with results. Hope we're going the right direction finally!
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VRCM also controls the fan so, yes I believe we're on the right track.
IF SO, you need to drive that car to houston and come take me to hooters!
*LMAO*
 
XLRVIII said:
VRCM also controls the fan so, yes I believe we're on the right track.
IF SO, you need to drive that car to houston and come take me to hooters!
*LMAO*
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I'd say we can definitely make that happen! FYI: a friend had a couple vcrms laying around from another year. Tried them and it Didn't work, but I'll wait and get the correct one before passing judgement.
 
left field comin at you. why did the previous motor pop a head gasket? could it be possible the converters are clogged?? the car should still run somewhat even with clogged converters, but it might be worth a check. the converters that are on it, did they come off the blown motor?
 
blacklsc1 said:
left field comin at you. why did the previous motor pop a head gasket? could it be possible the converters are clogged?? the car should still run somewhat even with clogged converters, but it might be worth a check. the converters that are on it, did they come off the blown motor?
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Great observation! The previous owner told me that the belt broke and the water pump wasn't pumping causing it to overheat. Yes the original converter on the side with the blown gasket was ruined as a result of water in the exhaust AND it was replaced during the swap. In fact, the only way it would run at all before was to loosen the O2 sensor on that side to releave the back pressure. The exhaust flow, as far as I can tell, shouldn't be a problem now.
 
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