Mustang won't start.

black88coupe

black88coupe

Club Member
I have my 85GT which has been converted to 1988 model EEC 4-SD. When the temp. gets below about 40deg's. it won't start. It will crank just fine but won't fire. If I manage to get it started it runs fine. On a warm day it will start up and run like a normal EFI car. I was going to replace the computer since I have a few spares on hand to see if that helps since it's easy to do. It's a factory SD harness that has been modified by eliminating the EGR and some other smog stuff. Otherwise it's pretty much factory. If any modifications were made to the harness the connections were soldered and shrink wrapped. Nothing was half assed on the harness. Any ideas?
 
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There is a cold start function in the EEC that gives high idle. If that was bad it could cause an issue

It has to read off of something.
 
No, something sends the EEC a signal to put motor into cold start mode. I'm just not sure what tells it too
 
The ECT sensor is the signal used to tell the processor what the temp is. The only real way to know if it's seeing a signal that is out of skew is with a scan tool. The old EEC is pretty simple but unless you can see what it's reading your just shooting in the dark.
 
94 Drop said:
The ECT sensor is the signal used to tell the processor what the temp is. The only real way to know if it's seeing a signal that is out of skew is with a scan tool. The old EEC is pretty simple but unless you can see what it's reading your just shooting in the dark.
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Thanks. I've got a spare ECT and was going to swap it out. It's pretty simple to change so I was gonna give it a shot.
 
My coupe had a pms on it, removed ect for a auto meter temp gauge. And it would still go into cold start
 
Idled perfect, accelerated perfect, made 480 to the wheel with a vortech.
Made more than that with a single 72mm turbo
 
Sounds like it needs more pulsewidth at lower temps in the cranking pw vs ect. Or as stated, the ect is screwy. I'm assuming stock injectors and sd tune? Do you have any tuning device? With a multimeter ohm out your ect first. Stick it in the freezer for a while, stick it in a pot of boiling water, or under the tap while gradually warming the water up and see if it follows around these readings. There is only about a 10ohm difference from what a stock a9l recognizes as the max temp @ cold start to around 40°. I don't have a clue about sd tunes.

ect.JPG
 
When it wont start, did u check for spark and fuel?......maybe you've got moisture in your tank and its freezing a line or a filter, could even be moisture in the DIST. cap causing ice on the points the rotor touchs......does it even sound like it wants to start?
 
Instead of just swapping parts have you used a scan tool to see what the engine coolant temp is reading when it will not start? If it's 28*F outside and your coolant temp reads 40 or 50*F the injectors will not be pulsed hard enough to overcome the increased air density. Think of it as a electronic choke as temp goes down choke increases until combustion chaimber temps and engine temp increase. Sometimes a bad connection or a bad wire will cause the sensor to read incorrect temps. Also you mentioned modifying the controller, does the coolant temp sensor have the correct resistance for the software in the controller? This all goes back to hooking up a scan tool and reading what the controller is seeing.
 
nitrouspete said:
When it wont start, did u check for spark and fuel?......maybe you've got moisture in your tank and its freezing a line or a filter, could even be moisture in the DIST. cap causing ice on the points the rotor touchs......does it even sound like it wants to start?
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It has about 40psi when I hit the key and I can smell gas after it cranks for a bit. It feels like its getting spark as it seems like it wants to start. I have been too busy to get really in depth with it right now. The sensor swap was a quick deal so I tried that to see if it would hopefully be a quick fix. It did fire right up after replacing the ECT but nothing after sitting overnight. Thank you very much for the input.
 
Polak said:
Instead of just swapping parts have you used a scan tool to see what the engine coolant temp is reading when it will not start? If it's 28*F outside and your coolant temp reads 40 or 50*F the injectors will not be pulsed hard enough to overcome the increased air density. Think of it as a electronic choke as temp goes down choke increases until combustion chaimber temps and engine temp increase. Sometimes a bad connection or a bad wire will cause the sensor to read incorrect temps. Also you mentioned modifying the controller, does the coolant temp sensor have the correct resistance for the software in the controller? This all goes back to hooking up a scan tool and reading what the controller is seeing.
Click to expand...
Like I mentioned above I haven't had time to get really in depth yet. The car runs great once it's running. I thought about a bad wire in the harness as well but it runs so good otherwise. I didn't modify the controller- just the harness itself. Thank you very much.
 
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