Wierd starting issue
Oct 15, 2018 7:58 PM - 304 Views Create A New Thread
Got me baffled
I'm having trouble with the starting of my '37. It's a GM Factory 430 hp crate engine, but the cam has been changed to a Comp Cams Thumper cam. The car has never been on the road, but the engine has been broken in on the engine dyno and has run in the car. It has a Holley electric fuel pump, which I also have questions about. I've had it running and have set the total timing to 34 degrees with the vacuum advance disconnected (highest hp on engine dyno). It has the factory HEI distributor. I've tried starting it with no gas pedal, with half pedal and with full pedal and it doesn't want to start on its own, but if I put an ounce of gas or a quick shot of easy start down the carb, it will start right up on the first turn. It runs rough for a minute or two then seems to smooth out pretty well. Once it has warmed up like that, you can start it all day long on the first turn without priming the carb. I've watched down the carb (not running) and when I work the throttle I can see fuel going into the carb. The odd thing though is that if I turn the key on without trying to start it and watch the fuel pressure regulator, it reads 6 lbs pressure, but after it runs for a few minutes, it starts to drop on the gauge and after 5 minutes or so it shows almost no pressure, but keeps running alright. Its got me a bit baffled, any ideas. Thanks, Bill
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Oct 23, 2018 at 9:06 AM
- Hi Jim, it turned out it wasn't a pressure problem, it was the fact that the pressure gauge was glycerin filled and the gauge wasn't vented. I drained about half the fluid and drilled a 1/16 hote in it for venting, now it reads the pressure steady at 6 lbs. The pump itself is about a foot from the tank, with the inlet of the pump, below the bottom of the tank and the tank is well vented, that's what was throwing me. I have mechanical pumps on my other two cars, first time to have an electric pump on a hot rod.
Oct 23, 2018 at 8:54 AM
1. Is tank vented ? If vented thru cap, is hole clogged ?
2. Where is pump mounted ? With in 2 feet of tank ? Level with tank ? Bottom or top fed fuel line ?
3. Electric pumps are pushers, not pullers.
I HATE electric fuel pumps...unless IN THE TANK. I am a Carter electric pump fan since 1957, if exposed.
No problems, no fun with hot rods.
Jim, School of Hot Rod Hard Knocks since 1957.
410 535 1933
Oct 19, 2018 at 8:48 AM
- The filter is new, so is the tank, but it's either that or the pump, which is also new.
Oct 19, 2018 at 8:03 AM
- I had this problem at one time. It turned out to be a bad fuel filter. I see you will look at that next.........
Oct 18, 2018 at 7:16 PM
- Willie, you were right. I changed the accelerator pump and all is good, starts like a charm. Now I have to figure out why my fuel pressure drops off after it runs for a few minutes. Tonight I let it run long enough to drop to 3 lbs, then shut it off, let it sit for a minute and put the key back on without starting it and the pressure wouldn't come back above 3 lbs, but if I let it sit for few hours, it will come back to 6 when I start it. I wondered if it wasn't venting properly, so took the cap off, no difference. It's a new tank, pump and filter but I'll check the filter next, seems like the flow is restricted somewhere.
Oct 16, 2018 at 7:17 PM
- Willie, I think you may have hit the nail on the head. On my '33 I can move the accelerator pump arm upclose to a 1/4" (it's a Quick Fuel Q950). On the '37 the diaphragm in the accelerator pump seems to have hardened up, as I can't push up on the arm at all. I took the diaphragm out of the carb and the rubber appears to have hardened up and has no flex in it. The carb is a new 770 Holley Street Avenger, but it sat on a shelf in my shop for probably close to 10 years before I used it. I'll pick up a new diaphragm and see if that cures my problem. I assume I can buy just the diaphragm.
Oct 16, 2018 at 1:12 PM
Check this out, it has the adjustments you need for the accelerator pump.
Oct 16, 2018 at 11:08 AM
- Before you start it go look inside the carb and open up the choke and pull the throttle see if gas is squirting in from the accelerator pump . If no gas that's a problem
Oct 16, 2018 at 9:09 AM
- I've tried changing the pressure regulator gauge, still the same.........6 lbs when not running, then gradually dropping off as it runs. Shouldn't affect the start though. I'll check the accelerator pump, tied up for the next 2 days, but I'll get to it by Thursday unless I can squeeze in a few minutes somewhere. There seems to be very little to no travel in the accelerator pump arm, as if it's stuck or something, so maybe that's it. How much should the arm move in itself?
Oct 16, 2018 at 6:33 AM
- You mentioned Holley electric fuel pump ,do you have a fuel pressure regulator with it ? while its running no pressure on the gauge sounds weird ,try a different gauge, 5-6 lbs. is about the norm maybe more for a Holley ,second accelerator pump
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