Rebuilt 302 won't start
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Trailering
Joined: Mar 2020
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Rebuilt 302 won't start
I just finished rebuilding the 302 in my 1990 f150 and I used a cam from a mustang so to fix the firing order problems I rewired the injectors. Things went perfectly and it fired right up on the first try so we were going over it checking everything and I could hear a little vacuum leak so we started and stopped it 3-4 times while changing things but then it randomly stopped working. it was running and I sprayed a some starting fluid around the throttle body to check for a vacuum leak and it stalled the motor and now it won't start at all. It has fuel, compression and spark but all it does it crank. Turning the distributor doesn't change anything and I messed with timing for a while with no change. Any idea of what the problem could be?
Hotshot
Joined: Jun 2015
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The simple answer is that the computer doesn’t care. It fires one set of four injectors and then the other four. It was posted here recently which set of four but I cannot find the thread right now. The only thing you needed to do was change the firing order on the distributor to the 302HO/ 351W firing order. Another couple of possible issues: What distributor gear are you using? The ‘90 truck cam was a flat tappet cam and I’m assuming the Mustang cam is a roller? If you reused the truck distributor gear it won’t live for long. Also what Mustang cam? The SD system might not be happy if you chose the wrong camshaft.
https://www.ford-trucks.com/forums/1...to-302-ho.html
https://www.ford-trucks.com/forums/1...to-302-ho.html
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Trailering
Joined: Mar 2020
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its a stage 2 tfs cam which I already know needs mass air and im planning on doing the swap but my friend and I just wanted to start it with speed density to see if it would work and it did, I'm just confused why it randomly stopped working. I also swapped the gear from a sn95 distributor onto the truck one.
New User
Joined: Mar 2020
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From: North Shore KIIIIID
Since it needs a MAF conversion, and this is known, maybe once the o2 sensors warmed up enough to put it into closed loop, the computer tried pulling (or adding way too much) fuel and set that as the baseline, and now you have a no start. Just a theory. I remember some Honda models not starting because of a bad coolant temp sensor throwing an irrational value into a speed density algorithm. Similar to your condition.
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Lead Driver
Joined: Jan 2019
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From: N.W. Alabama
The simple answer is that the computer doesn’t care. It fires one set of four injectors and then the other four. The ‘90 truck cam was a flat tappet cam and I’m assuming the Mustang cam is a roller? If you reused the truck distributor gear it won’t live for long. Also what Mustang cam? The SD system might not be happy if you chose the wrong camshaft.
just to add/ask to cam install, what lifters did you use? What heads with that cam(0.565 lift) PTV clearance issues checked?
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Trailering
Joined: Mar 2020
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Also I left the battery off overnight and when I tried things this morning it fired right up so my guess is that the computer reset itself and worked again so tomorrow I'll switch the injectors back and see if that fixes it. Today was spent fixing a blown trans line and a few other small things.
Lead Driver
Joined: Feb 2002
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From: Greater Austin, Texas
I put a 1990 302 in my son's 1995 F150 and changed the firing order back to the old one, did not change the injector wiring at all. It's been running fine for several years now. I used the original 1995 ECU.
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