Realized this is way too long for most to read, so here's the abridged version:

-Intermittent problem w/ van staying running
-Starts first crank every time, but will stall out after 20 seconds up to 20 minutes
-Ran perfectly prior to installation of a new electric fuel pump and elimination of manual fuel pump (plated off) - not sure if there's a correlation here or not
-Just tuned it w/ new plugs, wires, cap, rotor, pcv
-Have blown out the fuel lines front to back, attempted to power off an external gas tank, even removed exhaust thinking it may be plugged - no luck

Help!

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Long version

Greetings all. New to the forum w/ a 1977 Ford E250 hi top camper van w/ a 460 an 79,000 original miles. I picked it up from an elderly gentleman who used it as his fishing rig. It's been used sparingly for the last decade - 3000 miles or so. His health was in decline, thus the reason for sale. She's in great shape in and out. Here's the problem:

Drove like a champ on my 30 mile drive home. Started right up and had no issues. Decided to bring it to the shop to get the fluids changed - oil, coolant, brake fluid. Also had them look it over. They said it had a leak at the manual fuel pump and fuel line was a bit rotted in that area. Also said the electric fuel pump that had been installed was a cheapy and recommended replacement and plating off manual fuel pump as they couldn't find a replacement (said it was on national backorder). Ok, fine. Go ahead.

Picked it up, drove home (4 miles) w/ no issues. Gave her a tune-up (plugs, wires, cap, rotor, pcv). Took her out for a spin and it ran great. Decided to see how she'd do under heavy load and gave her a good womp on the gas. Not long after it began to sputter then stalled. Ever since then, it will start up like a champ, first crank, run for a bit, then sputter out. Sometimes it takes several minutes (10-20) then it'll die. Sometimes it will start and stall out w/in 20 seconds.

Brought it back to the shop. Long story short, they reached my financial cut-off point at which time they still didn't solve the issue. Blew out the lines, tested the fuel pump, hooked it up to an external gas tank, even disconnected the exhaust thinking it may be plugged. Still nothin. Next steps were to drop the tank to see if a vent was blocked (I kinda thought this would be a 1st step, but what do I know) then rebuilding carb (quoted 500-800). At that point I pulled the plug.

W/ all that said.... any ideas? I'm at a complete loss. Shoulda abided by the 'if it ain't broke, don't fix it!' rule from the start I think! Thanks in advance for any help/advise.

 

How long does it take before you can restart the van?
A cheap clear inline fuel filter will allow you to see if there is no fuel getting to the carb.

Check for spark as soon as it dies, before pursuing further fuel problems.

 

If I wait 20 seconds or so, it'll crank back up right away. It'll then sputter and die. I do believe fuel is getting to the carb as the mechanics pulled the supply line to it and ran the electric pump - gas was flowin'. I'll check for spark as suggested. Thanks!

I did some sleuthing and saw that someone w/ a similar issue and it was suggested it was the ignition box. Although it the stalling was more related to when the engine heated up, which doesn't seem to be the case w/ mine. Something to look into though I suppose.

 

20 seconds isn't a lot of time for testing!
Intermittent problems are the most difficult to diagnose.
Feel the coil and ignition box and see if one of them is very hot.

Test the resistance of various components.

Without knowing which system (fuel/spark) is causing the problem there's no point in excluding either.

But it seems you've gone pretty far looking into the fuel system.

 

Tinkered some more today. Tried starting this morning. Same issue. Starts then sputters out immediately. Tried again this afternoon. Would stay running w/ choke on full then it I pressed the gas OR tried to take off the choke it would die. Tested spark after stall and it was fine.

Removed air cleaner and just started poking around some lines. Noticed that a vacuum line that goes from dist cap to the pastic vent that attaches to the air cleaner had an extention tube installed for some reason and it was a little loose. Tighted it up. Tried to start - fired like a champ and ran like nothing was wrong. Out of curiosoity, I plugged said vac line and it made no difference. Removed the extention piece just in case. No idea if there was a correlation or if it was just coincidence.

As of now, it's running as normal. Will try again tomorrow. Could this be a vacuum issue? I'm also going to pull the fuel line going to the carb and remove the threaded inlet to see if there may be something in the screen. At that time I'll put an inline fuel fitler as well.

 

Do you have a vacuum routing diagram on your radiator support or drivers side valve cover?
(not sure about a truck of this vintage)

I have never seen a vacuum line connected to the distributor cap, nor coming from the air cleaner housing.

The proper vacuum diagram would help resolve the mystery.

I can say that on my truck the air cleaner's plastic crankcase filter connects to the breather, and the distributor vacuum advance unit connects to a thermal valve on the thermostat housing.

Maybe your mechanic is not at all familiar with older carbureted engines and added the 'extension' because they didn't know where else to put it?

There really should be only one fuel pump.
A mechanical pump on the timing case -or- an electric one.

You say you gave it a tune up.
Where did you set the ignition timing with the distributor advance vacuum line disconnected and plugged?
Did you reset the curb idle when you re-connected it?

 

Thanks for all the help ArdWrknTrk. Went out there today w/ high hopes that she'd start up, but back to square one. It'd start w/ full choke, then stall almost immediately. So odd how random this is.

Also, apologies for the poor description on my part. The described line doesn't go to the dist. cap, but somewhere just beneath it on the distributor itself I believe. I picked up a Chilton and it labels the line as "fresh air duct".

When I gave it the tune, all I did was replace parts (plugs, wires, cap, rotor, PCV). I didn't do any other adjustments to timing, etc.

There is only one fuel pump - inline electric installed in lieu of the mechanical pump.

I know just enough mechanically to make me dangerous and I've about reached my limits. I'll check the diagram, assuming it's in the areas described, but I'm not sure I'll know how to decipher it. I do agree that the shop I took it too, in retrospect, likely wasn't too up on the old carb technology.

Frustrating problem for sure. When it starts up and actually runs, it runs fantastic! It just doesn't start consistently! I'll keep trying.

 

It could always be some weird coincidence, but more likely something was done that caused this.

If this was a later truck that came with electric pumps and 'Hot Fuel Handling' I would say it was the oil pressure switch or the fuel pump relay.
But -obviously- this truck originally came with a mechanical pump on the timing case, and the electric pump is an afterthought.

(Your mechanic is pulling your leg if he says "the manual pump is on national backorder" )

If the van sat around a long time the carb could be full of sludge and your 'womp on the gas' lodged something in the jets.

Whatever,
It seems to be related to manifold vacuum.
... runs on full choke, and dies any time you try to open the throttle.

You say it was getting spark.
This would narrow it down to just fuel.
And since everything up to the carburetor checks out, I would then consider rebuilding it.

Next time you have the air cleaner off look for an aluminum tag screwed onto the carburetor with a part number on it.
Or try to see if there are some numbers stamped into the front (up where the choke flap fits)
I have no idea what carb would have come on a '77 E-250.

With the choke open, work the throttle while looking down into the carburetor and see if you can see a stream of gasoline in both front barrels.
if the accelerator pump is not working it will fall on its face and die when you open the throttle.

 

Thanks again. Did some more troubleshooting today. Fuel is getting TO the carb just fine. Removed the threaded module on the carb that the gas line goes into and it seemed to be fine. Ran the fuel pump and she cranked through no problem.

I can't see well enough to know if there's gas spraying in the carb as you hit the gas. It looks wet in there, but I can't actually see the spray. Even tried a mirror.

But now we have a new data point. I put some ether to it and she fired right up. Not only did it fire up, but it stayed started. Even under throttle it stayed running. Also gave it gas while braking to put it under a load... stayed running.

I'm going to let it cool and try again tomorrow and see what happens.

Any idea why the ether would have gotten it to not only start, but stay running? Regardless, I'm going to see how much a mechanic would charge to rebuild the carb as I think you are right about it likely being gunked up.

 

I wasn't thinking about how tight this engine is, in a van.

No, I'm sorry, I have no explanation as to why a shot of starting fluid would get your camper to run and stay running.

Try driving it with some fresh gas and maybe a bottle of injector cleaner.
If there's no further problems you may save yourself $200 or more.

 

The pendulum has swung again. Went out this evening and she won't stay running, even w/ the starter fluid. While it was running earlier I did put some Stabil gas treatment in (although it's fairly fresh gas) just in case. Let it run for about 20 minutes.

I will say that I can at least keep it running if I keep squirting some starter fluid in it. Combining that w/ the fact that when it does run, it runs great (no issue w/ spark, timing, etc I'm assuming), would it be safe to say that the problem most likely is in the carb? Or are there still other likely culprits... say, vacuum issue?

This sure is a head scratcher.

 

I can't think of anything other than some sediment in the bowl that has been sucked up.
There are a lot of people on this forum more knowledgeable than me.
I don't even know what carb would be on your '77.

Kinda surprised your mechanic didn't open it up and look while he had everything else apart.

 

I am too. I know where I won't be taking my rigs in the future.

I found a 'carb-aware' mechanic and it's going in for assessment on Friday. Likely a carb rebuild. It's a Motorcraft 4350 4 barrel carb. This new mechanic commented that it wasn't a particularly good carb on its best day and it'd be about $250 to rebuild/tune. He suggested spending a bit more for a new Edelbrock 1406 which he indicated would provide better, longer lasting performance. I'm thinking that, assuming the issue is the carb, I'll go w/ the Edelbrock.

I'll keep the thread posted. And thanks again for your help. Much appreciated.

 

Watch your fuel pressure with the Edelbrock.
I know you have a new electric pump.
You may need a fuel pressure return regulator if it is showing much above 5#.

 

Just a thought but some elec pumps need to be located back by the fuel tank to push the fuel to the engine rather then pull it up. They will bring up enough fuel to start and run but not enough to stay running. Good luck with it.