Hard starting new Walbro 255 early model 2 to 1 pump conversion

[dnguyen1963]

I think that after the first crank, the pistons creates enough negative pressure (vacuum) to pull the elbow in tight; thus eliminating the vacuum leak. Second crank starts normal because there was no more leak. As the car runs, there was enough vacuum to maintain a tight sealed engine. The cycles starts again after the car was stopped. This problem is more pronounced when the engine is hot.

[rcfanatic]

I had a smoke test performed this morning and it came back negative. Fuel pressure is 45 psi at idle.

Any other ideas about what would cause hard starting when warm?

[603Racing]

Just to verify, how did they perform the test? Some shops will connect directly to the throttle body. If this is the case, you could still have a leak at the elbow/boot.

Just for fun you could try a different DME if you can find a spare one. It's something very easy to try just to rule that out. I doubt it's the DME though.

Another easy/cheap test would be to do a noid light test on the injectors. This will verify that they are pulsing while you do your "first start" cranking when your car will not start.

Curiously... Does your CEL work? Do you have any codes?

[rcfanatic]

Smoke test was done at the entrance to the elbow.

Noid light would be easy but might be grasping at straws. It will start first try when warm, maybe 50% of the time. What bugs me is that no one else seems to have this problem with their aftermarket (non-check) pumps.

I have a 173 DME and late model cluster, but the CEL does not illuminate because the harness is early model.

[603Racing]

I wouldn't say grasping at straws. If the noid light tests pass then you know you're getting good signal from your CPS, the DME is working, and the injectors/injector harness are working.

You stated 45psi. Is that when cranking while the car is doing it's no start thing?