Will not start after changing distributor backfires through intake

KEVIN LOVEJOY

MEMBER
1999 GMC SUBURBAN
5.7L
V8
4WD
AUTOMATIC
130,000 MILES

I had a mechanic change my distributor for me. Found it would start yet not run, changed fuel pump then it ran but rough and had to keep at 1700 rpm to run, or it would cut out and shut off. I asked him to tune it up after changing out the pump (for some unknown reason he thought it was not starting and turned the distributor 180 degrees. Then he burnt up the starting trying to start it). This was so frustrating I waited six months to work on it again! I put a new starter in. Now it will not start at all so the mechanic put piston one at top end then moved the distributor to one. Still will not start just backfires through intake. (Does not even act like it is going to start) The mechanic got frustrated and put the old distributor back in yet put the new cap and rotor on it. (Said he never liked how the new one lined up, it was off 1/8 of a turn?) Since then I have personally removed the distributor, set piston one at top and put the starting point on the distributor at one. Still backfiring through intake it acts like it does not even want to start just backfiring through the intake "ugh"(do not know why the mechanic did not just leave the new one in there and turn it back around 180?)
Now I am beside myself trying to figure out what to do. I believe I put cylinder/piston one to top. I viewed it with a small bright LED and a mirror. I could see movement in the spark plug hole, yet could not really tell if it was the valves, cam or piston? When metal looked closest I stopped turning the engine, a screw driver would not go in very far so I figured that must be it. (I have checked the plugs, checked the firing order and all cables etc, are set correctly, checked the fuel and pressure "all good", took off air flow sensor, cleaned with AF cleaner, and checked all fuses). Am I missing something here? Please let me know and "thank you so much for your time and attention in this matter."
Kind regards, Kevin

1 Reply

CARADIODOC

MECHANIC
33,754 POSTS

You never once made mention about top dead center, on the compression stroke. Piston number one may be on the exhaust stroke, meaning the distributor is off 180 degrees.

The other problem that is real common, even once the distributor is in correctly, is the terminals under the cap do not line up with the terminals on top that the spark plugs wires go to. You have to look at the numbers molded on top of the cap, right next to the terminals, to know which cylinder that plug wire goes to. Getting these wrong is a real common cause of back-firing and a failure to run.

What was the original problem that made you think it needed a distributor? Obviously, if it was not starting for the mechanic, he had reason to believe the distributor must not be in right. Did that no-start possibly have the same cause as what you are fighting now?

Chrysler distributors can be installed correctly or 180 degrees off. Ford and GM distributors use a drive gear on the distributor's shaft. Those can be installed at least a dozen different ways. You need to get piston number one at top dead center on the compression stroke, then follow from terminal number one on the top of the distributor cap, to the terminal underneath by following the molded trail in the plastic. As you install the distributor, the shaft is going to turn due to the helically-cut gear. You need to try repeatedly until the tip of the rotor is under the correct cap terminal when the distributor is fully-seated.