86 bronco
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86 bronco
need some help. my son was driving his 86 bronco when it just died on him and wouldn't start. we got it towed back to the house and can not get it run without the timing being way advanced. originally we thought it had jumped the timing so we ended up replacing the timing chain which had not jumped at all. nothing seems to jump out as being the problem. we also checked for a vacuum leak but haven't found any yet. any ideas on what to look for?
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Did you remove the SPOUT when checking the base timing?
I would also suggest to remove the distributor and look very closely at the roll pin on the distributor gear. More than a few times that pin has sheared.
I would also suggest to remove the distributor and look very closely at the roll pin on the distributor gear. More than a few times that pin has sheared.
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Joined: Dec 2007
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From: Boise, Idaho
Which engine do you have? Is it carbureted or fuel injected?
Only the 302 was fuel injected in '86, the 300 and 351 are both still carbureted. (I'm assuming not the 300 since those don't have timing chains).
Double check that your harmonic balancer hasn't slipped. With time, the vulcanized rubber that holds the outer ring and the inner ring starts to lose its grip and the outer ring can slip. When it does, your timing mark is no longer pointed at 0.
Bring the #1 piston to TDC. If you can, shine a light down the spark plug hole and visually confirm that the piston has come all the way to the top. Otherwise, you can put a screwdriver or something in there and watch it move up and down. Rotate the engine until the piston is completely at the top.
Then, look to see if your timing mark is at 0. If it's not, you need a new harmonic balancer. It'll also be very difficult to time since the timing mark is no longer correct.
Otherwise, you can try timing it by vacuum. Put a vacuum gauge on the intake manifold and adjust the timing until you get the very best vacuum reading you can get. Then, back it off by about 1 1/2hg.
Only the 302 was fuel injected in '86, the 300 and 351 are both still carbureted. (I'm assuming not the 300 since those don't have timing chains).
Double check that your harmonic balancer hasn't slipped. With time, the vulcanized rubber that holds the outer ring and the inner ring starts to lose its grip and the outer ring can slip. When it does, your timing mark is no longer pointed at 0.
Bring the #1 piston to TDC. If you can, shine a light down the spark plug hole and visually confirm that the piston has come all the way to the top. Otherwise, you can put a screwdriver or something in there and watch it move up and down. Rotate the engine until the piston is completely at the top.
Then, look to see if your timing mark is at 0. If it's not, you need a new harmonic balancer. It'll also be very difficult to time since the timing mark is no longer correct.
Otherwise, you can try timing it by vacuum. Put a vacuum gauge on the intake manifold and adjust the timing until you get the very best vacuum reading you can get. Then, back it off by about 1 1/2hg.
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