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In tank electric pump coupled with new mechanical. TFI upgrade and tune up last year. New fuel filters last year. MSD ignition.

Just now developed a new quirk.

For the past couple of weeks, upon start up after warmed, the engine would fire, then stumble and die.

The more recent times, I've stood on the accelerator while cranking to see if it helps. Once, it helped. Last time it didn't Tried again. Had a nice loud backfire. Lots of fuel smell that time. Might have flooded it a bit.

I was leaning toward ignition timing, but the very last time, it was a cold start. One pump of gas like normal. Fired right off, then stumbled. Nearly died, then roared back to life. I'm leaning toward carb or fuel delivery issues. No issues otherwise such as cutting out while driving, lack of power, etc.

First of all having a mechanical pump with the electric pump in the tank isn't the best idea in the world. Bypass the mechanical pump for a start. Then go through the basics. Set timing to 10 degrees and set idle screws to 5 turns from seated. Maybe bump up the idle rpm a little just to try to get it to idle. If nothing helps a carb rebuild is in order.

kansasboy001 wrote:First of all having a mechanical pump with the electric pump in the tank isn't the best idea in the world. Bypass the mechanical pump for a start. Then go through the basics. Set timing to 10 degrees and set idle screws to 5 turns from seated. Maybe bump up the idle rpm a little just to try to get it to idle. If nothing helps a carb rebuild is in order.

Nothing wrong with a fresh mechanical teaming with the electric. It has run fine for a year like this. The electric addition was for vapor lock issues.
The big issue is running an old mechanical with electric. You can blow out a diaphram.

Should have mentioned the basics have all been covered last year.

Timing has been dialed in perfectly. Even have done vacuum gauge fine tuning for mileage improvement.

5 turns out on enrichment screws? That would run extremely rich. It was that way when I bought it. Your eyes would burn from the exhaust.

Enrichment screws are set at about 2 1/4 turns out, and it is still just a tad rich, but has run fine since.

Idle rpm is already a tad high.

Should also note it does eventually start with some persistence, but not like it has and should start normally.

Up till a few weeks ago, it would start with no throttle application and a short crank and fall right to idle when warmed.

Decided to try a cold start.
Normal cold start is one pump, fast idle cam engages, fires up on fast idle.


This time, start, then stalled.
Cranked again. Start, and stalled.
Second accelerator pump. Start, stalled.
Third pump. Started and ran on fast idle.

So, I'm having to pump the accelerator more than normal to start it.

I'm thinking you float is sticking. Back when I had a 2150 the float would stick in the closed position when it sat. But would be fine once it was running. A new needle and seat fixed the problem.

kansasboy001 wrote:I'm thinking you float is sticking. Back when I had a 2150 the float would stick in the closed position when it sat. But would be fine once it was running. A new needle and seat fixed the problem.

This could make sense. I tried this am and it started beautifully with one pump. Got it to operating temp, shut it off, waited 10 minutes (like I ran in and out of a store) and it started with no fuss. I'm thinking running some fuel system cleaner through it. If it still gives issues, I'll go deeper. If it needs a full rebuild at some point (it is only a couple years old reman) I'll start gathering GM TBI stuff.

Thanks for your help.

It needs some coffee.

csuengr wrote:It needs some coffee.