Slow Car Fast
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June 3, 2012 - Hang on a second, the tank is supposed to be in the car.
The car was running just fine...until I had it backed out of the garage and it died. No fuel pressure. I jacked the car up there and started running diagnostics. Of course, the first thing you suspect is the thing you just did. But because it was such a pain to weld the tank back together, I started looking elsewhere.
And I found something. It appeared that the regulator had died on me. When I disconnected it, I got a good gush of fuel out of the pump. Huh. The regulator is built in to a stock Corvette fuel filter that should be good for extended use - but maybe something from the tank plugged it. So I swapped in a new one. Nope. The pump struggled to get up to 40 psi (slowly) when it should have popped up to 60.
So I plugged a new hose on to the pump inlet and dropped the other end into a bowl of fuel. Voila, instant 60 psi. I'd tried this earlier without success, but I think I had the bowl too low so the pump couldn't suck it up. So out the tank had to come.
When I cut the top off, I didn't see anything obvious. But plugging the end of the pickup and blowing in the other end revealed the problem. A small pinhole in the new line where it had been tackwelded to the interior baffle. Not much, but once the pump was pulling hard it let in air instead of fuel. A half second zap with the welder and the pickup line was nicely airtight. Argh.
Welded it all back up again, smeared liquid metal around the seam again (to cover any pinholes in the welds) and the tank went back in. I tested it with a couple of gallons in the tank and again, 60 psi. Excellent.
Then the car refused to start. It cranked and backfired, then went "clunk" and wouldn't crank anymore. I'd been working the battery pretty hard during testing, so I threw on the charger. Just to check, I stuck a test light on a hot terminal in the engine bay. Nothing. Hmm.
I checked across the battery terminals, no problem. I checked from the grounding point to the terminals, no problem. But then I checked from the bumper to the battery. Nothing. Closer inspection showed that the main grounding point (a bolt running through the sheetmetal) was a bit loose. I tightened that up and all of a sudden I had power through the car.

If you remember back, the car's had the habit of not always starting on the first attempt. It would backfire and pop, and then would fire happily if I just cycled the key. It also had a habit of occasionally stopping at the side of the road. I'm thinking the loose ground strap may have been the culprit for the first, although we'll see if that behavior continues. The latter might have been related to that heavily restricted return line inside the tank. That's certainly not a problem before. We'll see what happens now. At the moment, the car is on "close to home" probation.
tags: fuel, troubleshooting, wiring