305 to 350 tbi swap

**Georgechevydude** · 05-31-2012, 12:45 AM

Put a 350 in my 87 GMC R10 and is cranks but doesn't start! When I bought the engine it ran great before I pulled it. I hear the fuel pump come on and I have a new regulator. I disconnected the fuel lines and gas shoots out. When I turn the key on the check engine light is on and stays on when I crank it. I did swap PROM chips too. It was before a 305 tbi with TH 400 and is now a 350 tbi with TH 400. I'm just not getting fuel out the injectors! I hooked up a noid light and nothing happen. I did hook up my DVOM and I am getting power to the injector connector but no ground pulse. I've even tried with the TPS disconnected just in case the ecu thought it was flooded. I've even tried another ECU and nothing still. I do get spark and when I put gas in the tb it runs and sounds smooth. All the fuses are fine, all the grounds and connectors are plugged up like they should be. The harness is fine. All I can think of is it off time real bad, the distributor modular is bad, the ecu is bad, bad pickup coil, or messed up wire. Please help!

**RB04Av** · 05-31-2012, 03:08 AM

If you "have spark", can't be anything about the dist or "timing" keeping it from getting fuel.

Pour a little gas into the intake; if it's a fueling problem, it should run until that fuel runs out.

Make sure you have the dist sending spark to the #1 plug at #1 firing, NOT at the OTHER instance of #1 TDC during an engine cycle which is when the #1 exh stroke is ending and its intake stroke beginning, and #6 firing.

Put the original PROM back in and see if it at least runs.

Once you get that far, swap PROMs.

One change at a time...

Logic. Reason. Patience. ;)

**Georgechevydude** · 05-31-2012, 08:16 AM

When I put gas in the throttle body is done run smooth. I am getting nothing out of the injectors not a drop! I have put the obd 1 plugin in diagnostic mode and the only code I got was code 12 which verifies its in diagnostic mode. Tried with the original PROM same thing. Both work in similar truck. When my truck had the 305 the distributor modular gave out. Think I'm going to get it tested and get a good look at the pickup coil.

**RB04Av** · 05-31-2012, 06:31 PM

LOGIC:

If there was something wrong with the dist, how would it run by pouring gas in it?

"The simplest explanation that fits all the facts is usually the right one". In this case, concentrate on the "fits all the facts" phrase... if your proposed explanation doesn't do that, IT'S WRONG.

Leave the dist alone and work on the fuel system. ;)

**Georgechevydude** · 05-31-2012, 07:44 PM

Originally Posted by RB04Av

LOGIC:

If there was something wrong with the dist, how would it run by pouring gas in it?

"The simplest explanation that fits all the facts is usually the right one". In this case, concentrate on the "fits all the facts" phrase... if your proposed explanation doesn't do that, IT'S WRONG.

Leave the dist alone and work on the fuel system. ;)

(SOLVED)Found the problem - it was the pickup coil which hooks into the distributor modulator. The wires was stripped so it was grounding to the distributor itself instead the injectors. I put in a new pickup coil and my baby fired right up! FYI the distributor also sends a crank signal to the ecu to fire the injectors. As the dist spins, the pick up coil builds up magnetism and grounds the system to the module and then to the ecu and then the injectors to ground and pulse.

**RB04Av** · 05-31-2012, 07:47 PM

So then, it DIDN'T run with fuel in the TB? We can't help you accurately if you don't tell us what's REALLY going on.

Because the pickup coil being fornicated would have prevented any spark - which is triggered from THE EXACT SAME PULSE FROM THE PICKUP COIL as the fuel - from occurring.

LOGIC.

**Georgechevydude** · 06-01-2012, 08:36 AM

Originally Posted by RB04Av

So then, it DIDN'T run with fuel in the TB? We can't help you accurately if you don't tell us what's REALLY going on.

Because the pickup coil being fornicated would have prevented any spark - which is triggered from THE EXACT SAME PULSE FROM THE PICKUP COIL as the fuel - from occurring.

LOGIC.

Yes it did run with gas in the throttle body! The firing in the distributor does have something to do with fuel (sends signal to turn on injectors and pulsation). Read the first post again.