'87 Suburban won't start after cap and rotor change

[ctb619]

Recently purchased a 1987 V2500 Suburban with a 350 TBI. It has been nothing but trouble so far, but I'm not quite ready to give up on her.

I had it running really well after swapping some parts and fixing a vacuum leak. My mechanic recommended I replace the spark plug wires and make sure they are routed away from the exhaust manifold. While I was at it, I decided I might as well replace the cap and rotor.

Well, now it won't start. I'm getting spark at the plugs, and I've checked the order on the distributor cap about 10 times to make sure the firing order is right. I tried going back to the old cap and rotor to see if the new parts were faulty, but with no success. I think it has something to do with the timing but I'm not exactly sure where to go from here. Any ideas?

 

[Jims86]

Hi Tyler, and welcome to GMSB.
did you loosen the hold down bolt on your distributor at all?
If not, I would keep looking at the wires, even a seasoned mechanic can cross 5 and 7 every now and then.
You may want to have somebody crank it while you look at the injectors, as they rely on a pulse from the ignition system for operation. If your wires are routed correctly, I would look to the 4 wire plug that goes into the distributor cap(ignition module)and make sure there is nothing broken, and it is plugged in all the way. You will still get spark if it is unplugged, just no timing control or fuel.
and make sure you didnt knock the vacuum line off of the MAP sensor.
Where in Ca are you?

 

[89Suburban]

You could also be a cylinder off in where you started the wire sequence at. Pull the #1 cylinder plug and find TDC on the compression stroke to see where the rotor is pointing.

That's a damn good lookin burb, don't give up on her!

 

[ctb619]

Hi Tyler, and welcome to GMSB.
did you loosen the hold down bolt on your distributor at all?
If not, I would keep looking at the wires, even a seasoned mechanic can cross 5 and 7 every now and then.
You may want to have somebody crank it while you look at the injectors, as they rely on a pulse from the ignition system for operation. If your wires are routed correctly, I would look to the 4 wire plug that goes into the distributor cap(ignition module)and make sure there is nothing broken, and it is plugged in all the way. You will still get spark if it is unplugged, just no timing control or fuel.
and make sure you didnt knock the vacuum line off of the MAP sensor.
Where in Ca are you?

I didn't touch the hold down bolt on the distributor. Re-traced the spark plug wires again and everything checks out. All the wires and the connections going into the distributor look good. Vacuum lines check out. I'll see about taking a look at the injectors tomorrow. I'm in North County San Diego. Thanks for the feedback, Jim!

 

[ctb619]

You could also be a cylinder off in where you started the wire sequence at. Pull the #1 cylinder plug and find TDC on the compression stroke to see where the rotor is pointing.

That's a damn good lookin burb, don't give up on her!

I considered that, but I tried shifting the plugs one position in each direction and got the same result. To check TDC on compression stroke I turn the pulley until the timing groove is lined up with 0 degrees on the timing tab? I'm a bit intimidated by the process as I've never done it before. Thanks for the advice.

 

[wildcatjason]

If wanna be sure your wires are right which I'd be surprised if they are go buy a 30 dollar timing light double check.

 

[ctb619]

If wanna be sure your wires are right which I'd be surprised if they are go buy a 30 dollar timing light double check.

I have one. I didn't even realize you could use a timing light on an engine that won't run. So just follow the normal procedure and check the timing while someone cranks the engine?

 

[wildcatjason]

If there's a spark sure, but if number one is right and if you have any other wires wrong it won't fire but the timing will look right.

 

[ctb619]

Thanks, Jason. I'll give it a try.

 

[Swims350]

if you got sprak dump some gas down the tbi and see if it fires up. If so you got fuel issues.

 

[ctb619]

So I threw a timing light at it, and the timing doesn't seem right (but it was difficult to tell with how slow it was moving). I'm going to find TDC to make sure the rotor is pointing at the #1 cylinder and #1 spark plug wire. I've never done this before, but as I understand it the transmission should be in neutral prior to turning the crankshaft pulley. Anything else I need to do with wiring before checking TDC?

 

[ctb619]

She's alive!!!!! I took everything apart, and put it back together, and this time the truck started . I wish I knew what was causing the problem, but it's certainly nice to have it running again. The next hurdle is to get it to pass smog

Thanks, everyone

 

[wildcatjason]

So I threw a timing light at it, and the timing doesn't seem right (but it was difficult to tell with how slow it was moving). I'm going to find TDC to make sure the rotor is pointing at the #1 cylinder and #1 spark plug wire. I've never done this before, but as I understand it the transmission should be in neutral prior to turning the crankshaft pulley. Anything else I need to do with wiring before checking TDC?

Honestly if you haven't pulled the distributor finding TDC shouldn't be necessary. Just to clarify the timing order is 18436572. There are two forward plugs on the distributor. #1 is on the driver side forward one. Go clockwise. #1 is on the drivers side. All the even #'d cylinders are on the passenger side, odd on the drivers. If you feel it necessary to find TDC. I pull the #1 plug put a screwdriver in it and then pull the rotor cap to make sure you're on the compression stroke not the exhaust. When the timing mark is lined up, the rotor is pointing to the #1 and the screwdriver is all the way up. You're at TDC. If you have difficulty turning the engine with a wrench. Pull all the plugs to relieve its compression and yes put the vehicle in neutral. Hope that helps.

 

[wildcatjason]

She's alive!!!!! I took everything apart, and put it back together, and this time the truck started . I wish I knew what was causing the problem, but it's certainly nice to have it running again. The next hurdle is to get it to pass smog

Thanks, everyone

Good to hear!