Fuel Issue on my 69 RR

jimm69 · May 10, 2017

Since you all were so awesome helping me with my starter issue, i have another issue.

the car ran good last summer with the exception of the vapor lock issue. Now I seem to have another fuel issue. I have a fairly stock 440 with an edelbrock 800 on it. the car seems to need a prime all the time to get the car started unless it is warm. I disconnected the fuel line at the pump and ran a hose to a bucket and no fuel comes out. disconnected line from tank and held finger over the input fitting and I do not feel and suction at all. I have a holley pump that I put on it last summer. I know it puts out (or at least used to when I had a gauge on it). I no longer have a gauge because I switched to the stock steel fuel line from pump to carb so there is no room for a gauge. Is there a way to check the pump before ditching it for a new one? i was also told that the rod that pushes on the pump could have been replaced with a cheap product when the motor was rebuilt. I do not know and the builder has since passed so I can not ask him. is there any way to check any of this?

PurpleBeeper · May 11, 2017

I'm confused..... you put on a holley ELECTRIC fuel pump? Do you have a mechanical fuel pump on the engine? electric only? both mechanical & electric?

"needing a prime" on a car with a carburetor is 100% normal.

gkent · May 11, 2017

PurpleBeeper said:
"needing a prime" on a car with a carburetor is 100% normal.

NOT TRUE. Unless the carb has percolated dry it should have fuel in it and should not need a prime. Fuel can't drain out of a carb.

gkent · May 11, 2017

You can put a vacuum gauge on the pump to check it. They're pretty cheap at Harbor Freight, etc.

jimm69 · May 11, 2017

Stanton said:
You can put a vacuum gauge on the pump to check it. They're pretty cheap at Harbor Freight, etc.

I never used to have to prime the car before. Just started this after the winter. The car has a holly mechanical fuel pump mounted to the block. purchased new at summit almost 2 years ago, but probably doesn't have more than 500 miles on it. now, it seems as if the car even sits overnight that it has to be primed with gas dumped into the carb. I pulled the fuel line outlet off and run the hose into a bucket and nothing comes out. I pulled the inlet off and held my finger over the fitting and don't feel any suction. I put my vacuum gauge on the inlet (not sure if this was the right thing to do) and get no vacuum reading at all. not sure if that was the proper way to check. assuming that there is no suction, than I believe 2 things could be the cause. number one would be a bad fuel pump. if that was the case, not sure why it would run if I primed the carb and got it started. the other thing could be the push rod for the fuel pump could be bad. again, not sure why the car would run if I primed the carb.

a few other things to note are when I test drove the car yesterday, it idled fine and ran really well and mild acceleration. If I really got on it, it bogged way down until it could catch up. also last summer, I had issues at what I believed to be vapor lock. when sitting in traffic idling when the outside temp was hot, car choked out and could not be restarted until hours later. when this happened, I pulled feed line to carb off and got nothing out of the pump. also pulled line off the pump and got nothing out of it either. just chocked it up to vapor lock but now not so sure. want to try to diagnose before buying another fuel pump because pump was not cheap (around $130 at summit).

PurpleBeeper · May 11, 2017

Stanton said:
NOT TRUE. Unless the carb has percolated dry it should have fuel in it and should not need a prime. Fuel can't drain out of a carb.

I see your point, but my six pack has a "vent" on the center fuel bowl that allows fuel to evaporate & my electric-only fuel pump is mounted above the tank. Also, of all the 30+ carbureted Mopars I've owned over the years, ALL of them required 2-3 gas pedal pumps before cranking to start.....just saying.

For Jimmy69.... I will assume that someone was cranking the engine over when you ran your mechanical fuel pump tests, right? Then you've got it figured out. Either the pump or the pump rod isn't right.....or a real long shot... the fuel pump lobe on the cam (99.99% not the problem). I guess the only other thing I can think of (since the pump is new) is maybe you've got a pinhole fuel line leak somewhere? That might make the pump suck air for a few seconds. Otherwise, pull the pump, inspect the rod & fix what's broke......sort of sounds like the pump though if you don't have a leak.

Another thing you could do is buy a $10 junkyard fuel pump to run a test before you plunk down $130

gkent · May 11, 2017

1) I believe those pumps are rebuildable

2) "usually" when a pump goes bad it develops a leak in the diaphragm and you'll have fuel leaking all over the place

3) I think the bog is unrelated. If there is enough fuel to run then there should be plenty of fuel to handle acceleration - at least instantly without causing a bog. If it accelerates then bogs, that would indicate fuel starvation. But it would take a bit to run the float bowls dry.

4) now you mention you "primed the carb". To me this means you poured gas down the carb - and the engine started and ran. To me this indicates the pump works fine - otherwise, where did the fuel come from?!

5) depending on your winter storage method, it might be wise to look at the carb as the issue. Possibly dirt or tried up fuel residue plugging things up.

jimm69 · May 11, 2017

Stanton said:
1) I believe those pumps are rebuildable

2) "usually" when a pump goes bad it develops a leak in the diaphragm and you'll have fuel leaking all over the place

3) I think the bog is unrelated. If there is enough fuel to run then there should be plenty of fuel to handle acceleration - at least instantly without causing a bog. If it accelerates then bogs, that would indicate fuel starvation. But it would take a bit to run the float bowls dry.

4) now you mention you "primed the carb". To me this means you poured gas down the carb - and the engine started and ran. To me this indicates the pump works fine - otherwise, where did the fuel come from?!

5) depending on your winter storage method, it might be wise to look at the carb as the issue. Possibly dirt or tried up fuel residue plugging things up.

Stanton....

1) I can look into a rebuild kit if I determine the pump is bad
2) I have no fuel leaks at all
3) You are probably correct about the carb. I had a Holley on the car and did not have any bogging issues. I recently changed to an edelbrock that I got from a buddy because I was having the vapor lock issue and wanted to go with a stock steel fuel line from pump to carb. My buddy did play around with springs and rods in the carb when he had it. So, I am convinced that I probably need to try to put those back to factory. I just threw that out there as additional info in case it might matter.
4) You are correct. I had to pour gas into the carb to get it to start. Once I did this a time or two, the car was running under its own fuel.
5) I put Sta-bil in the tank when stored. Carb that car was stored with has been replaced, so not sure that is the issue

If the carb is good, how can there be no vacuum on the inlet side and no suction? Can this be an intermittent problem? Is there another way to test the fuel pump? should I remove it and bench test it to check for a possible bad push rod?

lewtot184 · May 11, 2017

i would pull out the fuel pump push rod and check it. make sure you don't have a canister/cellulose type fuel filter on the suction side of the pump. mancini sells pump rebuild kits for carters. i bought one once; very poor quality.

jimm69 · May 11, 2017

PurpleBeeper said:
I see your point, but my six pack has a "vent" on the center fuel bowl that allows fuel to evaporate & my electric-only fuel pump is mounted above the tank. Also, of all the 30+ carbureted Mopars I've owned over the years, ALL of them required 2-3 gas pedal pumps before cranking to start.....just saying.

For Jimmy69.... I will assume that someone was cranking the engine over when you ran your mechanical fuel pump tests, right? Then you've got it figured out. Either the pump or the pump rod isn't right.....or a real long shot... the fuel pump lobe on the cam (99.99% not the problem). I guess the only other thing I can think of (since the pump is new) is maybe you've got a pinhole fuel line leak somewhere? That might make the pump suck air for a few seconds. Otherwise, pull the pump, inspect the rod & fix what's broke......sort of sounds like the pump though if you don't have a leak.

Another thing you could do is buy a $10 junkyard fuel pump to run a test before you plunk down $130

Purplebeeper....yes, wife was cranking the motor while I checked the pump. what I don't understand is how the pump could appear to not be sucking anything but yet the car could run after you dumped gas in the carb (not talking about initial burst, but it would continue to run.) with a mechanical pump, could it have intermittent failure? I believe the rod would either work or not work. it can not be intermittent.....same with cam lobe, right?

lewtot184....I do not have any type of filter before the fuel pump....other than the boot in the tank.

lewtot184 · May 11, 2017

another thing to check is all the hose connections on the suction side of the pump/fuel lines. any cracks/loose connections will screw up the fuel flow.

jimm69 · May 11, 2017

lewtot184 said:
another thing to check is all the hose connections on the suction side of the pump/fuel lines. any cracks/loose connections will screw up the fuel flow.

I have checked that already even though new steel lines were installed as well as new rubber connecting steel to tank and steel to pump

furyus · May 11, 2017

My 64 Sport Fury was having the same issues. I bought a new pushrod. Checked it against the one in the engine. Same size. The car would start, but if I pushed on the gas, it would bog, and stall. Of course it did this 3 hours from home. At the Daytona Turkey Rod Run. I drove it gently, and it got me all the way home. I also heard the pump rebuild kits were crap, and when I looked at the pump lobe on the cam, it didn't look too good. Looked worn, and not very tall. So without knowing how tall the lobe was supposed to be, I went with an electric pump. My suggestion is to pull the rod, as already mentioned, and check its length. If it's fine, I would call a cam company, and ask how tall the pump lobe should be. If those check out, then you get to decide what to do with the pump.

gkent · May 11, 2017

You're cranking the engine over at maybe 100 RPM ... when it starts its idling at around 800. That would generate more suction - even on a defective pump.

As for the cam lobe thing, I would expect lifter lobes to be toast before a fuel pump lobe - not trying to worry you, just stating a fact - there's a lot more load on a lifter than a fuel pump rod.

jimm69 · May 11, 2017

Stanton said:
You're cranking the engine over at maybe 100 RPM ... when it starts its idling at around 800. That would generate more suction - even on a defective pump.

As for the cam lobe thing, I would expect lifter lobes to be toast before a fuel pump lobe - not trying to worry you, just stating a fact - there's a lot more load on a lifter than a fuel pump rod.

wouldn't you think that a vacuum test would show some vacuum while cranking it? if I take the pump off and manually push it, I should get some vacuum, right? that would show me if it was the rod or cam lobe, right?

gkent · May 11, 2017

Cam lobe - I'd pull the pump and turn the motor over by hand while holding the pushrod in with a screwdriver.

I think you'll find the pump is VERY hard to push manually. That spring in the pump has to be strong enough to keep the pushrod riding the cam up to 7000 rpm !! Like wise, getting the pump back in came be a real bitch for this same reason!

I'd be looking at every other possibility before I pulled the pump.

gkent · May 11, 2017

You have no evidence of a leak.
You have fuel when the car starts and runs.

You have to prime the car - indicates no fuel in the carb or accelerator pump section.
Car "bogs" - also a possible symptom of an accelerator pump issue.

Maybe turn your focus to the carb - at least its easier to get at!

oldbee · May 11, 2017

Jimm, speed has nothing to with it, ur right 1 stroke pulls vacuum & pressure going out the outlet just a whole faster. I would've thought you'd be able to feel something on a finger held in the inlet fitting. I personally have never heard of a cam lobe for fuel wearing down, just not enuf pressure on it.

lewtot184 · May 11, 2017

the fuel pump lobe is not like the tappet lobes. it's a complete circle on an eccentric. the fuel pump push rod is always in motion. i've had push rods wear out without any damage to the lobe.

i do test fuel pumps using a spare block/camshaft/cam gear/push rod/pressure gauge with pump attached to the block. i spin the cam with a drill motor (single bolt cam) and check pressure and volume.

Dennis H · May 11, 2017

Define "Prime?

Fuel Issue on my 69 RR

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