Help Diagnose my Fuel Problem

Cupid

Member
Mar 30, 2006
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My setup is in the signature:

My problem:
-I don't know if i'm getting enought fuel.

What I know:
-I have a new Holley Fuel Pump(Model HLY 12-854)
-I have a new 1411 Eddy Carb, tuned to the best of my abilites with a Vacuum gauge
-I have approx 9" of vacuum @ 800 RPM. I've checked for leaks with carb cleaner and can't find any relative increase in RPM when I spray. Some say 9" is good for my size Cam:shrug:
-My RPM bounces between 800 & 1200 RPM while sitting at idle
-When I get on her, especially at WOT, If I push the clutch in to come to a quick stop, she dies.
-I have a hard time starting her if she sits for about 10 -15 minutes after coming up to operating temperature.
-I notice my clear fuel filter is empty.....a lot, but only when I shut the car off. When i'm about 1000 or so RPM, it's half-way to full. Normal???
-Perhaps the weirdest of all......there is *no* hesitation at WOT....whatsoever, this freaking thing accelerates like a rocket!

What I think:
-My fuel filter should be full all the time???
-At low RPM my pump doesn't produce enough fuel pressure for starting the car???
-When I come down from high RPM all the fuel gets sucked down, b/c my pump doesn't produce enough fuel at low RPM???

Enlighten me please...
 
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Are you running a fuel regulator? I would suggest getting a fuel pressure guage installed so you can monitor (from the engine compartment) what is happening at different RPM's. I think it is pretty common for the fuel to go back down in the fuel filter once the engine is shut off. You should have enough fuel left in the carb boals for the car to start back up and refill the bowls. A common problem that results in the hard to start after driving symptom is the fuel in the bowls boils from the heat coming off the intake manifold, causing evaporation. Are you funning a spacer between the carb and the intake? If so, what is the material? Where are your heater hoses routed? If near the carb, I would move them away. Actually, check for heat sources anywhere near the fuel line as well.
 
I think you need to double check the rest of your engine sttings. I'm going to assume that the timing gear set is new, and that you disconnected the vacuum advance when you set your timing? 10 degrees overlap isn't enough to cause a 4k rpm fluctuation while idling.

When you snap the throttle from under the hood, does it respond like it should?

Your fuel filter will NOT be full all the time. I think you need to go back over the basics of your tune.
 
IMO, sounds like a vacuum leak. There are other sources of vacuum leaks such as auto transmission and brake boosters.

I was curious about your vacuum reading. My mild Crane Cam pulls 12 inches at idle, I looked up your Edelbrock cam on their website and noticed the following:

"CAMSHAFT: Performer RPM Hydraulic
CATALOG #7168
ENGINE: Ford 351 c.i.d. Cleveland V8
RPM RANGE: 1500-6500
CAUTION: Do not use dual valve springs. Use appropriate valve
springs which will accomodate the lift of the camshaft. Use stock ratio
rocker arms only."
 
Still having the hard start problem....

Notes:
- Bought a phenolic washer
- Set timing at 17* (engine turns over fine)
- The RPM fluctuation was due to a faulty TACH
- Cannot find a vac leak anywhere, 9-10" of Vac @ 800 rpm
- When car is running, it's virtually perfect, throttle response is very crisp
- Engine temp does not exceed 190*
 
As suggested earlier, it's back to the basics time.

Gas, air and spark need to be checked. Even if you suspect heat issue, holding down the gas pedal will eventually start the engine, or should.

Wait till engine is cool, disconnect gas line from carb and place in an appropriate container. Just tap the key and watch for gas coming out of pump. You shouldn't have to tap too long, even with a stock pump. You need to have more caution with a high flow pump. Make sure you have plenty of area ventilation as gas fumes are very explosive.

Don't laugh, but I've heard of clogged air filters killing engines.

Having the proper spark is a guessing game as from experience, it could be good one minute and bad the next until what ever is causing the problem totally fails.

On a side note, when you say that your idle rpm bounces between 800-1200, does that mean that the tach needle is literally bouncing consistently or that it would idle at 800, then 1200 later? If it is the later, mine does the same thing with no hard start problems. If the tach needle bounces all the time, it could be a bad electrical connection.

Good luck.
 
As suggested earlier, it's back to the basics time.

Gas, air and spark need to be checked. Even if you suspect heat issue, holding down the gas pedal will eventually start the engine, or should.

Wait till engine is cool, disconnect gas line from carb and place in an appropriate container. Just tap the key and watch for gas coming out of pump. You shouldn't have to tap too long, even with a stock pump. You need to have more caution with a high flow pump. Make sure you have plenty of area ventilation as gas fumes are very explosive.

Don't laugh, but I've heard of clogged air filters killing engines.

Having the proper spark is a guessing game as from experience, it could be good one minute and bad the next until what ever is causing the problem totally fails.

On a side note, when you say that your idle rpm bounces between 800-1200, does that mean that the tach needle is literally bouncing consistently or that it would idle at 800, then 1200 later? If it is the later, mine does the same thing with no hard start problems. If the tach needle bounces all the time, it could be a bad electrical connection.

Good luck.

Yes, holding the gas pedal down eventually starts it, followed by the black smoke..:rlaugh:

Dang it...forgot to mention that I put a guage on the fuel line. It is getting from 6.5 to 7 psi so I don't think that is the problem.

I'll swap the airfilter out to see if that's holding me up.

Spark is delivered via MSD 6AL (8 or 9 years old) and MSD billet Dizzy (brand new). I assume that's fine since I only have problems starting the car, but when she's running, she runs well.

Yes, using an old analog Sunpro tester, the RPM would bounce consistently, but now that I bought a new TACH, it hovers around 800 smoothly.

I honestly think I have all the basics covered! Funny thing is, I was having this problem before I rebuilt the motor. Of course everything is new now (with some additions).:rolleyes:
 
Spark is delivered via MSD 6AL (8 or 9 years old) and MSD billet Dizzy (brand new). I assume that's fine since I only have problems starting the car, but when she's running, she runs well.

AHA! I was having the same off and on no start condition with my old MSD6A unit. I eventually bypassed it and have not had a no start condition.

Be warned, that after the off and on no start condition, the car did die while driving off and on also. I changed the coil but problem still persisted. I have not had anymore problems since bypassing the MSD6A unit.
 
AHA! I was having the same off and on no start condition with my old MSD6A unit. I eventually bypassed it and have not had a no start condition.

Be warned, that after the off and on no start condition, the car did die while driving off and on also. I changed the coil but problem still persisted. I have not had anymore problems since bypassing the MSD6A unit.

Hmmmm....

So it could be my box huh? That just doesn't make sense though(no offense). I'm up for trying anything, but why would my box work perfectly only when starting the car up initially, but when bringing the car up to operating temp, leaving it for 30 mins, then stop working?:shrug:
 
When you shut the engine off look down the carb. Sounds like you are dumping fuel and flooding it out. That would explain the hard starts and black smoke. Could be sticky float. You said this happened with the old engine? Same carb?
 
When you shut the engine off look down the carb. Sounds like you are dumping fuel and flooding it out. That would explain the hard starts and black smoke. Could be sticky float. You said this happened with the old engine? Same carb?

I'll check to see if i'm dumping fuel.

It did happen with the old engine. I used the old carb when I first put it together and it did the same thing.

I bought a new carb since then....same type, just w/electric choke, and it does the same *exact* thing...
 
Really simple. Edelbrocks are notorious for boiling the fuel out of the bowls after driving. Only takes about 10 minutes. Both of mine have the exact same problem you describe.

Basically the engine is flooded. Floor it and crank until it starts.
 
Really simple. Edelbrocks are notorious for boiling the fuel out of the bowls after driving. Only takes about 10 minutes. Both of mine have the exact same problem you describe.

Basically the engine is flooded. Floor it and crank until it starts.
Maybe that's why the OEM carb to spacer & spacer to manifold gaskets are about 5/32" thick as opposed to the thin 1/32" ones that are supplied with most carb rebuild kits.