ok i swapped out my 2000gt motor with a 94 mark 8. the wires are extnded and everything is hooked up. i used the 2000 computer and wiringharness. i get fire and fuel but it wont start. it will backfire sumtimes through the intake. im completly lost to why it wont start. any help would be appreciated.
a lil help needed
- Thread starter lushdog1984
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wmburns
SN Certified Technician
Just wondering if you aren't expecting a little too quick of a "rescue". Patience. Help is here.
Since you are in such a hurry for help, please read and answer all questions.
Confirm that the theft light goes out after a key on 3 second "prove out" and does not come on during cranking.
Confirm that the motor grounding strap from the left hand motor mount to the frame rail has been installed.
Confirm there is +12 volts at all injectors with the key on. Have you confirmed an injector pulse with a "noid" tester?
What happens if the throttle is held have way open during cranking?
What happens if the MAF electrical connector is disconnected during cranking.
Explain what you did for the ignition. Where did the COP's come from? What spark plugs have you used?
Explain what was done to the motor before installing. What it re-timed? What are the results of a compression test? Backfire is usually associated with incorrect timing or a secondary ignition problem.
Do you have a Ford workshop manual, wiring diagrams, and PCM manual for your car?
Since you are in such a hurry for help, please read and answer all questions.
Confirm that the theft light goes out after a key on 3 second "prove out" and does not come on during cranking.
Confirm that the motor grounding strap from the left hand motor mount to the frame rail has been installed.
Confirm there is +12 volts at all injectors with the key on. Have you confirmed an injector pulse with a "noid" tester?
What happens if the throttle is held have way open during cranking?
What happens if the MAF electrical connector is disconnected during cranking.
Explain what you did for the ignition. Where did the COP's come from? What spark plugs have you used?
Explain what was done to the motor before installing. What it re-timed? What are the results of a compression test? Backfire is usually associated with incorrect timing or a secondary ignition problem.
Do you have a Ford workshop manual, wiring diagrams, and PCM manual for your car?
hotcobra03
Active Member
ok everything is factory. the cops and everything. the ground u talked about is not hooked up. as for testin the injectors i have not but they are all firing. thxs to pullin every plug to make sure. the timing has not been changed and timed with what the book said. idk what it was at the moment but it was dead on. i have the manuals and wiring specs. like i said everything is hooked minus temp sensor. anything else idk about
it has new plugs for the dohc. i no they have to be platinum or sumthin. um as to the theft light im not sure. im only sure i havent kicked the pats cause i do get fire. i talked to a ford tech and he said he would look into it. he also said that on these swaps some people are using the cobra processor. i have a computer for a 98 cobra but im pretty sure it wont work due to the coil on plugs im runnin instead of twin coils. so i dont understand why he told me that. id really rather not have to get a mark 8 harness and rewire everything up then have to change computers and have it flashed.
wmburns
SN Certified Technician
So you don't think not having an engine ground could be a problem? How would you suspose the spark would get back to ground?
I also recall reading threads about different COP being needed when the 99-04 GT PCM is paired with a 4V DOHC motor. Suggest searching some more.
The PCM from a 98 Cobra will NOT fit into a 99-04.
IMO, your problem is a missing ground and use of the incorrect COP's.
trinity_gt
10 Year Member
Which timing are you talking about here? Cam or ignition?
If cams -- if you had the front cover off and the chains out etc and put it back together -- are you extra quintupley double triple sure you got the cam timing correct and the parts all installed correctly (e.g. the timing wheel)?
If ignition, how was it timed "with what the book said"? Static timing is fixed by the location of the CKP and CPS and timing wheel and dynamic timing is set by the PCM. There is no manual adjustment required or even possible (unless you have a Steeda timing adjuster...)
Backfiring through the intake suggests a combustion event occurring while an intake valve is still open. So either the cam timing is off (e.g. an intake cam is retarded) or the spark is occurring at the wrong time (early).
How is the engine compression?
lol hopefully tommorow i will find out if the ground is the problem. i just figured since the coil packs were sparking then sumthin else was wrong. guess ill see tommorow. and about the coils i used some from a lincoln navigator and they worked fine when the gt motor was in it. im not sure if it matters but the numbers on the coils were different. i didnt have a problem with misfire or anything. i used 2 of them until i get buy replacement coil packs
wmburns
SN Certified Technician
Mark VIII DOHC COP polarity
You post here looking for help with your project. Some of us have taken the time to answer and requested more information. I have to say that the responses really don't cover what we are trying to find out. The Modular motor is a very difficult motor to time. It's not just a simple "line up the dots".
I have help 4 other ppl with builds presenting symptoms of a mistimed motor. All swore they had followed "the book" and had set it up correctly. After tons of diagnostic work, the mistimed motor was finally discovered.
I encourage you to double check your work. Did you take pictures when the timing chains were set up? It really won't take that long for you to describe how the motor was timed.
Please read the following thread regarding COP polarity (post #5).
98 mark 8 in 03 gt, do i need to swap the cop`s polarity ? - Ford Mustang Forums
This post is from someone that has actually done the swap and has first hand experience with the problems encountered.
Here's another thread with a ton of information and some great pictures:
Infamous Lincoln Mark VIII engine swap thread.
You post here looking for help with your project. Some of us have taken the time to answer and requested more information. I have to say that the responses really don't cover what we are trying to find out. The Modular motor is a very difficult motor to time. It's not just a simple "line up the dots".
I have help 4 other ppl with builds presenting symptoms of a mistimed motor. All swore they had followed "the book" and had set it up correctly. After tons of diagnostic work, the mistimed motor was finally discovered.
I encourage you to double check your work. Did you take pictures when the timing chains were set up? It really won't take that long for you to describe how the motor was timed.
Please read the following thread regarding COP polarity (post #5).
98 mark 8 in 03 gt, do i need to swap the cop`s polarity ? - Ford Mustang Forums
This post is from someone that has actually done the swap and has first hand experience with the problems encountered.
Here's another thread with a ton of information and some great pictures:
Infamous Lincoln Mark VIII engine swap thread.
ok the motor came from a wrecked mark 8 that had 33,000 miles on it. it has never been aprt other then the intake so i could fit the motor in the engine bay. no cams no nuthin has been put in. just a simple pull out put in motor swapp. and i greatly apprediate the help and info you guys are giving me. thanks. also i swapped the old valve covers for covers from the navigator. so if it is a timing issue it beats me. and we checked the timing with a timing light and i dnt remember the degree of timing but it was spot on with what the manual said a dohc mustang should be and if im not mistaken the timing was the same for the sohc as well.
wmburns
SN Certified Technician
wmburns
SN Certified Technician
Post #5:
98 mark 8 in 03 gt, do i need to swap the cop`s polarity ? - Ford Mustang Forums
>>From Bullitt5339
As someone who has worked through this issue before, here's the correct answer:
If you use the COPS from the 4V with the 2V wiring, yes, you need to switch the polarity. You can also trim down the tabs on the 2V COPS and use them as is. I just don't like the way they fit trimmed down.
<<
If you are asking HOW to switch polarity, didn't you extend the COP wiring? Seems you could switch the wires at the splice. Or remove the pins at the COP electrical connector and reverse them.
I'm sure what Bullitt5339 meant about triming the tabs was to remove the keyway from the COP and then turn the electrical connector upside down.
98 mark 8 in 03 gt, do i need to swap the cop`s polarity ? - Ford Mustang Forums
>>From Bullitt5339
As someone who has worked through this issue before, here's the correct answer:
If you use the COPS from the 4V with the 2V wiring, yes, you need to switch the polarity. You can also trim down the tabs on the 2V COPS and use them as is. I just don't like the way they fit trimmed down.
<<
If you are asking HOW to switch polarity, didn't you extend the COP wiring? Seems you could switch the wires at the splice. Or remove the pins at the COP electrical connector and reverse them.
I'm sure what Bullitt5339 meant about triming the tabs was to remove the keyway from the COP and then turn the electrical connector upside down.
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