jb442

iTrader: (4)

I've been troubleshooting a problem where my engine will randomly stall, typically, but not always, between 10-to-15 minutes after starting cold. Once it does stalls, you can usually start it up again within a minute or two. The car has even stalled while cruising at 80 MPH down the freeway - I put it in neutral and after three attempts, it started back up after I was down to about 60 MPH. Anyway, once the engine is restarted, I can usually finish my trip without a problem, even if it's 30 or more minutes longer. The majority of stalls have occurred at very low speeds, driving conservatively, mainly right after going from 1st to 2nd, although it has happened right off the line.

I’ve only had one instance where the car has stalled and I was able to get a fuel pressure gauge on it quickly. When connecting it, I was surprised at the lack of fuel pressure at the Schrader valve – It usually sprays out pretty good, but it was more of a “gurgle” this time. So, that was my first indication of a fuel issue. It took a minute or two to get the gauge on, and, within that time, the system had recovered because the pressure showed fine after the system primed. It then started right up, and I was able to continue driving to my destination.

I’ve data-logged a few trips and the computer never indicates there is a problem with any sensor, or sets any diagnostic trouble codes. I’ve checked the fuel pressure at various times, and it shows about 38 PSI at idle (vacuum line connected), and about 46 PSI (vacuum disconnected). Once the fuel rail is pressurized, it seems to hold the pressure as well.

The latest thing I’ve noticed, and maybe the most important thing, is noise at the pressure regulator: I decided to test out the pressure by manually operating the prime circuit for a few minutes. After a few seconds of running, I hear what seems to be an aerated fuel mixture running through the system. The pressure stays pretty close to where it should be, but it is definitely not a smooth flow of fuel through the line. I’m just not sure whether it’s most likely something wrong with fuel pump, pickup, etc. or the regulator. One thing I haven’t done is to simply disconnect the main fuel line flow it into a container so I can visibly see the fuel flow.

I’d appreciate any feedback from anyone who has dealt with a fuel problem similar to this. More info: The stock pump was replaced with a Racetronix Walbro 255 pump back in July 2007, so it's been in there for about 3.5 years and about 23,000 miles.

Thanks, John.

jb442

iTrader: (4)

I tried another fuel pressure regulator with the same results, so unless it's somehow the fuel filter (also 3.5 years old) causing the problem (which I doubt), there is some issue with the Walbro 255 pump. I know it came with the factory style flex hose, but how often are there issues with those? It sounds like the pump is picking up air and fuel. Now that I think about it, the lower the fuel in the tank, the more often it seemed to stall out. I'll probably pull the pump out of the tank next weekend. Does this seem like a premature failure for a Walbro pump (Racetronix) or about the normal longevity for them?

l 95 Trans Am l

iTrader: (5)

Could be something as simple as the fuel filter. Ask you this, when you installed the walbro did you use the supplied rubber hose? They are known to deteriorate after awhile, cracks in the hose can cause a loss in fuel pressure. Hope this helps, it sucks to have a mystery issue with a car. Good luck!

jb442

iTrader: (4)

I don't recall getting a rubber line with the Racetronix kit... I believe they included a factory-style pressure line. I think there are two other rubber hoses, and I just re-used the factory lines - For the vent and return line.

I'll try replacing the filter next, then I'll pull the pump out of the tank. I replaced the first pump by dropping the tank... This time, I'm going to use the access-panel method, which it seems about 95% of the LT1s here have done already!

l 95 Trans Am l

iTrader: (5)

Thats what I did the first pump replacement. I bought a chinese knockoff that I thought was a good pump, then it went out and when I had to replace it it was much easier with the access hatch, went with a Walbro that time.

jb442

iTrader: (4)

I believe I've located the problem... Bucket just split after installing the Racetronix Walbro pump 3.5 years ago. I remember using a LOT of glue on the bucket too, but it looks like it just wasn't enough. Maybe some of the fuel additives out here in California are to blame for weakening the glue. Anyone else have this happen to their bucket?

Split Bucket:

jb442

iTrader: (4)

Upon closer inspection of the bucket, the Walbro pump was still sealed at the bottom... So, the bucket splitting apart really didn't harm anything or cause an issue. I tried another pump in the car, and it's doing the same thing as the Walbro/Racetronix setup. So, the gremlin is somewhere else. I did notice that an unusual amount of pressure is building up in the tank. I'm now thinking that the fuel tank vent valve or carbon canister valve might not be working properly, and the vapor pressure in the tank is the source of my problem.