Difficult hot/wam restarts...Ethanol?

[blazer74]

I also have had the fuel pump issue, mine was to the point of having to hold the pedal to the floor to get the engine to start.

Seems like most aftermarket pumps put out to much pressure and heat soak makes it worse. Pressure In the lines increases with heat soak causing the pressure to overcome the needle/seat and flood.

I still have a slight hot start issue but nothing like it was.

Float level to high will also cause problems.

Air tex I think is one of the worst. Some can put out up to 9 psi which is too much. I plumbed In a gauge to see what the press actually was.

[brown7373]

Air-Tex "one of the worst".  Great...that seems likely to be my problem.  Oh well, fuel pumps are not really that expensive.

[von]

Yep "Air-Tex" was the brand I had. I had two of them before I rigged up a pressure gauge and found 9 psi running on one and 10 psi on the other. After shutting the fully warmed engine off the pressure would rise for a few minutes before slowly dropping.

[brown7373]

Air-Tex...Great, I also have one on my 70 Bonneville that I am rebuilding, so I may have the same issue when I get that back on the road.  I've owned the Bonne for 36 years.  I have always been able to just reach in and twist the key, like after a fill up, without even getting in the car.  It has always fired right up and idled fine.

[blazer74]

If you have the time and desire plumb in a pressure gauge and you will see the pressure issue. Gets to the point of overcoming the needle sometimes and flooding the engine.
Some run an a/c delco  pump for this issue.

[brown7373]

That sure sounds plausible.  It isn't flooded to the point that it won't start, but it does struggle some, and is worse when it is hotter, which would seem to increase the pressure a little more.

[brown7373]

My issues have continued and with warmer weather, a little worse.  I put on my old fuel pump this morning.  I replaced it because I thought it "looked" old, and I wanted to replace before it failed out on the road.  I noticed immediately that it seems to start much easier when hot.  Additionally, with the Air-Tex, I wasn't able to get the idle down around 600 in drive.  With the old pump, it idles smoother and I can adjust idle below 600 if I wanted to.  That seems on the surface to confirm it was pushing a little fuel past the inlet seat even when at idle, and certainly after shutdown.  I have not yet driven it enough to be positive, but so far that sure seems to correct the issue.

I still want to buy a new fuel pump (mechanical), but almost everyone sells Air-Tex.  Anyone know if anyone sells an AC Delco?

[von]

Airtex is the brand I had a problem with. I bought two of them before I realized  they were the problem. Even their specs show pressures that are too high for a Q jet.

[brown7373]

It seems like it is harder and harder to find mechanicals that are NOT Air-Tex.  Many of the parts stores in my area sell Air-Tex, including NAPA.  I also have one on my 1970 Bonneville 455 that I will soon be starting to break-in the cam.  I purchased an AC from ebay and plan to switch it today before I start the engine.

[Cliff Ruggles]

We have been getting a LOT of complaints to the shop in recent years concerning currently available mechanical fuel pumps.

One customer that we built two BBC Marine units for actually sent one of them back because it flooded after shut down, difficult to start cold or hot, and running issues.  We tested the carb and it was flawless, returned it to him, the troubles continued.  I had him swap the good working carb from the other engine and it started acting up.  Turns out the culprit was the "new" fuel pump, the other pump was also new, same manufacturer, and working fine.

So before replacing the pump he did a fuel pressure check, it was around 10-12 psi, not 5-6 like the other one......Cliff

[brown7373]

Ya gotta love quality control!