GSV Forum

The symptoms: Engine seems to catch, but doesn't run. If we keep at it, it'll catch on the 4th-6th try, but it will stall almost immediately. If I coax it with the throttle, I can sometimes make it race for a while, but if I let it drop towards idle, it dies.

We've checked the firing sequence, swapped the spark plugs with a different set, and played with the timing, but haven't been able to get any kind of reading with my timing light.

- Before we started it up for the first time, I force fed the fuel pump from the fuse box, and listened to the happy gurgling as it it purged air from the system. The fuel pump's revs dropped a LOT when all the air was gone. We don't have a fuel pressure meter (how many times I have wished I had one!), but I'm planning to drip a little fuel into the intake manifold before our next attempt, to see if that improves the behaviour.

- The replacement engine had been sitting for sale for a long time when we acquired it, and I'm wondering about the possibility of stuck piston rings. I guess I should take out the plugs and squirt some engine oil into each cylinder and spin it around with the starter for a while. (When we filled it up with oil, we did remember to put some of it in through the hole in the valve cover where the vacuum hoses attach). It has excellent oil pressure.
Thanks for all advice. Sigurd (my son in law) and I did three tests today, and think we have narrowed it down to a fuel delivery issue. What kind of fuel delivery issue still needs to be determined.

1) First test was to pull out a vacuum plug from the intake manifold, pour in 1 tablespoon of fuel, wait 30 seconds, and crank the engine. It fired immediately, and ran beautifully for about 5 seconds. This seems to rule out the possiblity of major problems in the ignition system.

2) Second test was to loosen the fuel rail from the intake manifold, place an egg cup under each injector, and run the starter motor for about 20 seconds. All 4 injectors delivered fuel. The quantity looked to be about the same in each egg cup. All in all we got about one tablespoon of fuel = the same amount that we had fed in and made the engine run for 5 seconds. Too little fuel?

3) Third test was to hold the fuel rail up under a strong light with a strip of clean folded paper towel underneath, run the the starter motor for 15 seconds, and study how the fuel came squirting out. I had expected it to be more or less vaporized, like when you squeeze the trigger on a spray bottle, but that did not happen. The fuel came out as tiny squirts of liquid. I could clearly (with my reading glasses) see the droplets as they travelled the inch or so of distance between the injectors and the paper towel.

My working hypothesis now that the problem is low fuel pressure, either from a faulty fuel pressure regulator or a faulty fuel pump. My guess is that it's the pump, but since it takes a fraction of the time to change the FPR, and I have several in stock, I should start with that?
After dinner, we disconnected the vacuum hose from the FPR to the intake manifold, at the manifold end. No fuel smell. Sucked on it hard. The FPR holds vacuum. Good.

Next step was to disconnect the return hose from the FPR, and to run the starter motor. No fuel came out. Either the FPR is failing to open (causing excessive fuel pressure in rail) or the pump can't produce enough pressure to make the FPR open. I'm guessing the latter.

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