'72 F100 stalls accelerating from stop, won't start after engine warm

[Maravich14]

Hey guys, any ideas?

Some issues, not sure if connected. 72 F-100 will sometimes stall when accelerating from stop and has to sit awhile ~20 minutes to start back up. The truck will usually start after sitting overnight, but not always. If shut off after warming up, it won't start back up again. Cranks but won't start. Edelbrock 1406 carb, HEI distributor. Has spark from each plug, fuel getting to carb and coming out squirters. When it won't start, there is always a strong smell of gas. Is it flooding? Idle mixture set too high? Sometimes though the fuel won't come out of the tank line, so I'll have to create suction for the pump to send it to the carb. Any help troubleshooting this madness is appreciated.

 

[ponymare]

The next time it dies, loosen the fuel cap and listen for a suction sound, that would be a plugged cap or vet tube. If you smell gas at the carb, it could be a bad power valve or some other internal fuel leak.

 

[tinman080]

Your fuel tank sock (screen) on the tank pickup may be about blocked up, causing intermittent fuel supply, disconnect your fuel line and blow a shot of compressed air(not too high a pressure)into the tank thru the fuel supply line with the cap removed. Make sure the tank cap is venting well. Your float level may be set too high, or the needle and seat is getting trash into it, causing flooding. Change your fuel filter, check your float for leaks (if brass, shake it while listening for slosh), adjust your idle mixture, but if it is that far off it would run so badly at idle you would hardly be able to run it at low speeds. Do you have the last 4 inches of rubber hose to the carb? If you do, be advised those hoses can start separating by layers internally and cause fuel delivery or trash in the needle and seat resulting in flooding problems. A mechanical fuel pump with a pinhole in the diaphram can drain down overnite making the vehicle hard to start. A diaphram-type accelerator pump can be bad, causing hesitation or stalling when increasing the throttle pressure. You sound like you have a flooding problem, remember the warmer the engine the Less fuel it needs to run, especially at idle speeds or when being started. Check your carb first, The rest of the suggestions are for fuel starvation issues. Make sure to clean or replace your plugs after these issues you've been having, deposits are likely. Best of luck! Gary

 

[Ole Don]

Two things to add to Tinmans words; if you buy rubber hose these days, you have to step up to hose marked "fuel injection" hose. It costs about three times more, but the old style will only last a year.
Two, check for vacuum leaks under the carb. An Edelbrock should always be on a spacer of some type to insulate it from heat.

 

[Maravich14]

The next time it dies, loosen the fuel cap and listen for a suction sound, that would be a plugged cap or vet tube. If you smell gas at the carb, it could be a bad power valve or some other internal fuel leak.

Will try that out, thank you

Your fuel tank sock (screen) on the tank pickup may be about blocked up, causing intermittent fuel supply, disconnect your fuel line and blow a shot of compressed air(not too high a pressure)into the tank thru the fuel supply line with the cap removed. Make sure the tank cap is venting well. Your float level may be set too high, or the needle and seat is getting trash into it, causing flooding. Change your fuel filter, check your float for leaks (if brass, shake it while listening for slosh), adjust your idle mixture, but if it is that far off it would run so badly at idle you would hardly be able to run it at low speeds. Do you have the last 4 inches of rubber hose to the carb? If you do, be advised those hoses can start separating by layers internally and cause fuel delivery or trash in the needle and seat resulting in flooding problems. A mechanical fuel pump with a pinhole in the diaphram can drain down overnite making the vehicle hard to start. A diaphram-type accelerator pump can be bad, causing hesitation or stalling when increasing the throttle pressure. You sound like you have a flooding problem, remember the warmer the engine the Less fuel it needs to run, especially at idle speeds or when being started. Check your carb first, The rest of the suggestions are for fuel starvation issues. Make sure to clean or replace your plugs after these issues you've been having, deposits are likely. Best of luck! Gary

Hmm, interesting. I do have about 3-4 inches of hose connecting the filter and carb. The filters, one near the carb and one between pump and tank, both looked warped internally, like collapsed. Thought the one next to carb was heat-warped until I saw one next to pump was warped too. Could too much PSI cause that? Not sure if my pump is diaphram type. Will have to post pics later today. Will work on the carb. Thanks for the wise words of advice, Gary!

Two things to add to Tinmans words; if you buy rubber hose these days, you have to step up to hose marked "fuel injection" hose. It costs about three times more, but the old style will only last a year.
Two, check for vacuum leaks under the carb. An Edelbrock should always be on a spacer of some type to insulate it from heat.

I was working on it last night, and it does have a spacer put on it, but I'll check everything again. The vacuum hose from the distributor to the carb was unhooked at the carb, so I plugged it back up. No change, but might have been other issues compounding it.

 

[miker98038]

All the above are possible causes, and I had all of them, one time or another in my 55 bird, with the 1406 carb. If your area has ethanol at 10% or more, that is likely the root of the problem. It dissolves junk in the tank, dissolves the old style hoses, the rubber in the fuel pump diaphragm, and even some older filter elements. I've had cars as late as 1992 develop fuel hose leaks for no apparent reason, with the pre ethanol hoses. At 40+ psi with fuel injection, that's pretty scary.

As you work thru this, keep Ole Don's advise in mind. Buy the hoses, filters, rebuild kits rated for the new fuel, if you can't avoid buying it. Not trying to be negative, but been there done that.

 

[Maravich14]

So done a little bit of work on it. Both fuel filters look collapsed like this. Gonna replace them and blow out the line. Took off the carb and gonna clean it. Hopefully that will do the trick, otherwise it could be pump related?

@Miker- My area indeed has 10% ethanol. I've tried to stay away from unleaded and get premium, as well as installing bio-fuel compliant fuel line, but the problem persists. Been dealing with contamination issues off and on the past year and a half. Had hose shedding in my Holley before switching over to the Edelbrock. It ran great, but rich, for a couple months, but now it's another issue. Thanks for your advice, truly. I can use all the help I can get.

 

[Maravich14]

Update: Replaced both filters, blew out line. After doing a bit more research, maybe the issue is that I haven't had a fuel pressure gauge on this Edelbrock the whole time. Read Edelbrocks like 4.5-5 PSI, but last time the pressure was checked, it ran in the 7.5-8 range. Think that's causing the issues?

 

[Motorhead6]

When it dies, pull a couple of plugs immediately. If the problem is too much fuel pressure, you should have wet plugs(fuel not oil). If so, check the float level in the carb. 7.5-8 psi should not cause it to flood unless the needle and seat are marginal or the float level is too high. Marginal needle and seat are very possible given that you are using ethanol laden gas. By all means, all older vehicles should get Sta-Bil Marine treatment for ethanol with every fill up. The combination of spark, fuel coming out of the squirters and the smell of gas all point to flooding. When the engine does start, there may be black smoke from the exhaust which would indicate flooding. It may also emit a little at idle. I think you are onto something.

If there is no indication of fuel on the plugs, then I would chase a distributor problem. I am not a huge fan of HEI's except that they are easy to wire up. Could be a coil or module breaking down when hot.

I really think you eliminated the fuel-to-carburetor delivery issue by the fact that there is fuel from the squirters and you smell gas up front.

 

[scicala]

I tend to disagree that 7.5 to 8 PSI isn't too high for the fuel pressure. A would say a max of 6 PSI and maybe 5 being ideal. I can't say this is contributing to you're issue, but just my opinion from a life long career in carburetion.

Also, what is going on with the right front barrel of your Edelbrock carburetor ? All of the black contamination looks like you have the PCV hose connected to the timed distributor vacuum port of the carb ?

Sal

 

[Motorhead6]

I do also agree that 7.5-8 psi is a bit high. Just not sure that bringing it down will solve the problem. Certainly worth a try since it really needs to come down a bit anyway.

 

[Maravich14]

When it dies, pull a couple of plugs immediately. If the problem is too much fuel pressure, you should have wet plugs(fuel not oil). If so, check the float level in the carb. 7.5-8 psi should not cause it to flood unless the needle and seat are marginal or the float level is too high. Marginal needle and seat are very possible given that you are using ethanol laden gas. By all means, all older vehicles should get Sta-Bil Marine treatment for ethanol with every fill up. The combination of spark, fuel coming out of the squirters and the smell of gas all point to flooding. When the engine does start, there may be black smoke from the exhaust which would indicate flooding. It may also emit a little at idle. I think you are onto something.

If there is no indication of fuel on the plugs, then I would chase a distributor problem. I am not a huge fan of HEI's except that they are easy to wire up. Could be a coil or module breaking down when hot.

I really think you eliminated the fuel-to-carburetor delivery issue by the fact that there is fuel from the squirters and you smell gas up front.

I'll try that plug trick next time it dies on me. I had been using Star Tron in the fuel but would put it in when I got home as opposed to putting it in the tank pre-fillup. I'll make sure to keep it handy. Haven't seen any black smoke out of the exhaust as of yet, but it's definitely running rich. I took the top off the carb, and cleaned out all of that gunk you're seeing. This carb was one I got from a friend, and I'm thinking that all that is a mixture of his crud and the crud from my tank. The jets were clogged so I blew them clean. I went ahead and slapped it back on and wanted to see if it could run before rebuilding it. It took a bit, but it finally revved up. Warmed it up and drove around the block just fine. Now I just have to adjust some things because it's very slow to accelerate to higher speeds. Might take it off and give it a rebuild/chem-dip if the problem returns. I'm starting to not like the HEI's either. Wondering if the truck dying when accelerating from stops could be related?

I tend to disagree that 7.5 to 8 PSI isn't too high for the fuel pressure. A would say a max of 6 PSI and maybe 5 being ideal. I can't say this is contributing to you're issue, but just my opinion from a life long career in carburetion.

Also, what is going on with the right front barrel of your Edelbrock carburetor ? All of the black contamination looks like you have the PCV hose connected to the timed distributor vacuum port of the carb ?

Sal

I'm probably gonna slap a regulator on there anyways. Rather be on the safe side than anything. I don't know if that contamination was on there from when it was on my friend's Maverick, but the distributor has been hooked up to the timed port on mine the whole time. Cleaned what I could without chem-dip.

 

[tinman080]

The accelerator pump, even if squirting may not be delivering the amount of fuel needed by your particular engine when increasing speed, resulting in a flat or dead spot when wanting to increase speed. Once the initial shot of fuel goes thru the venturi effect cuts in and draws required fuel to maintain a constant speed.. A carb can starve an engine when delivering metered fuel, and can flood on the same engine due to a float issue.....By looking at the photos this carb looks like it has had moisture in the bowls, the white corrosion on the bottom shows. And no, I am NOT a carb expert.....Sal definitely sounds like the man to hear.

 

[Maravich14]

The accelerator pump, even if squirting may not be delivering the amount of fuel needed by your particular engine when increasing speed, resulting in a flat or dead spot when wanting to increase speed. Once the initial shot of fuel goes thru the venturi effect cuts in and draws required fuel to maintain a constant speed.. A carb can starve an engine when delivering metered fuel, and can flood on the same engine due to a float issue.....By looking at the photos this carb looks like it has had moisture in the bowls, the white corrosion on the bottom shows. And no, I am NOT a carb expert.....Sal definitely sounds like the man to hear.

Thanks for the advice. I have a 302 engine on that '72, so not sure if it's getting enough fuel. May just be my paranoia, but it seems like I'm getting worse fuel mileage from the 4 barrel Edel as opposed to the 2 barrel Holley or the older carb (maybe Motorcraft). I'm no carb expert either, just a student, so maybe I just need to do some tweaking with the carb to get the best mileage. Would adjusting the idle mixture and speed screws do the trick? I'm a bit of a newbie, so I appreciate the tips.

Also, my apologies for the bad pics, that white you see is actually just shine from my camera flash. I had sprayed some carb cleaner in there before taking the pics I think, so that flash bounced off that.

 

[DrinkinGasoline]

Thanks for the advice. I have a 302 engine on that '72, so not sure if it's getting enough fuel. May just be my paranoia, but it seems like I'm getting worse fuel mileage from the 4 barrel Edel as opposed to the 2 barrel Holley or the older carb (maybe Motorcraft).

When I bought my 84 302 it had the Edel on it with horrible fuel economy regardless of what i did to it. I went back to the Motorcraft 2150 and all was well again. It took some adjusting and a manual choke but runs great and gets decent mileage. The M2100/2150 carbs are very easy to tweek-in and very reliable.