Now I’m really confused

[Doug&Deb]

To follow up on my fuel of ignition problem. I decided to try a different coil thinking it may solve the problem. No joy. Shut down at about the same time as always. The electric pump got me home again. Today I let it warm up completely in the garage while I checked everything. Timing is good, dwell is 38 degrees. All connections between the gas tank to the carburetor are clean and tight with no leaks. Took a long ride and no problems at all. The only difference: Friday was 82 degrees and today is 45 degrees. Seems like vapor lock but I’ve driven in much hotter temperatures with no issues. I should add that there’s no smell of gas in the oil so I doubt it’s the fuel pump. I’m really confused.

[Sam Buchanan]

Fuel pumps can get erratic even if the diaphragm is still good and not leaking gas into the oil. There are check valves in the pump that have to be fully operational for maintaining proper fuel pressure. Perhaps a valve has gotten weak and in combination with winter gas is losing prime (I don't know where you live). I still think that pump is screaming "Replace me!".

[Semmerling]

I must admit that now I'm really confused.

 

If in fact you were able to make it home (with the car operating normally) using the electric fuel pump then, may I assume that you could not make it home relying on your mechanical fuel pump? If that is correct then I agree with Sam.

 

 

[Doug&Deb]

You’re probably right but what does the temperature have to do with it? I’m in southwest pa so the gas in the tank is a mixture of summer and winter blend. Today with cooler weather it ran perfectly. The engine temperature was the same just the outside temperature changed. 

[keithb7]

Tying-in a fuel pressure gauge at the carb entry point could prove whats going on. A long enough hose, feed it up through the cowl area so you can temporarily watch it while driving. 

Go with the full mechanical pump and watch fuel pressure. Is it dropping when things get hot along with warm ambient air temp? When things act up, monitor closely. Then switch over to electric pump. Now what is the fuel pressure? Does pressure stabilize and symptoms disappear?  
 

If this proves nothing, then on to the next thing to test. 
 

Thinking I might also consider plugging/sealing up both ends of fuel line at various spots as needed. Pressure it up a few psi with a gauge. Then monitor pressure for leaks. This will confirm if you are or aren’t sucking air somewhere. 
 

 

Edited April 23, 2023 by keithb7

[Happy 46R]

I like Keith's comments for resolving the problem. I did however notice you mentioned vapour lock and ambient temperature in your post. Is there any chance that your temperature gauge is faulty and not registering your engine temp correctly? That would certainly affect what is happening with the mechanical pump and could confuse the trouble shooting. Am I correct in assuming you have the heat shield in place above the fuel pump? Just a thought.  Dave

[Doug&Deb]

Heat shield is in place. I have a Stewart Warner temperature gauge because the original gauge doesn’t work. I’ve verified the temperature readings with my infrared thermometer. I have to get a fuel pressure gauge and try that. Otherwise I think my head will explode lol.

[Booger]

I would think the E fuel pump would assist in any deficiency of the mech pump. Isnt that the point of installing one?  I mean if your getting a steady stream of gas down the pie hole...

[Happy 46R]

Sorry my ideas didn't solve your problem. Best I could come up with but I am hopeful you get an answer soon as exploding heads are messy to clean up. Probably something simple that everyone will say "Why didn't I think of that?" Good luck and let us know.  Dave

[Hickory]

A vacuum gauge is also a fuel pressure gauge, normally.

[DonaldSmith]

I'm trying to figure out how to plumb my fuel line for a test.  Either I need a coupling for a hose, to extend to a container for my 12 pulses for 8 ounces, or to add a tee for my vacuum/pressure gauge.  Stay tuned.   

[JohnS48plm]

Is your gas cap vented?

[Los_Control]

5 hours ago, Sam Buchanan said:

Fuel pumps can get erratic even if the diaphragm is still good and not leaking gas into the oil.

My experience with a bad fuel pump was on a 1993 Caravan with a electric pump in the tank

Father inlaw picked the wife & I up in Albuquerque Heading to Washington state. ..... He said he had a fuel issue on the way. Was strange.

 

Problem was we could drive all night in cool air but come about 10:00-11:00 AM, the black asphalt was collecting radiant heat, the fuel tank was heating up ... the pump would still run, but not move any fuel. ...... Were talking 80F-90F daytime temps.

 

Leaving ABQ the hottest part of the trip in the afternoon, we only made it a few hours til it crapped out on us. We waited til dark then drove all night into Utah.

 

Utah we had a bad tire, slept in the van at walmart, when they opened we got a new tire. It was a light rain that day, we were able to get almost to Idaho in the rain.

Then the weather cleared up the sun came out .... acted like vapor lock again.

 

We sat till dark. Then we made it into Oregon overnight, by 10:00AM-11:00AM it got warm ..... we hung out in the park all day like bums .... waiting for late afternoon.

We drove all night again and made it to our destination in WA the next morning.

 

We changed the fuel pump & never had the problem again .... We drove it from WA to TX a few times after that.

 

Only saying I have seen first hand how we drove 1/2 way across country with a bad fuel pump.

The OEM pump would not pump fuel when the weather got warm, work all day long in cooler weather. ..... We could hear the electric pump motor working.

Must have been something to do with the rubber diaphragm stretching when it got warm?

[Sam Buchanan]

 

24 minutes ago, Los_Control said:

My experience with a bad fuel pump was on a 1993 Caravan with a electric pump in the tank

Father inlaw picked the wife & I up in Albuquerque Heading to Washington state. ..... He said he had a fuel issue on the way. Was strange.

 

Problem was we could drive all night in cool air but come about 10:00-11:00 AM, the black asphalt was collecting radiant heat, the fuel tank was heating up ... the pump would still run, but not move any fuel. ...... Were talking 80F-90F daytime temps.

 

Leaving ABQ the hottest part of the trip in the afternoon, we only made it a few hours til it crapped out on us. We waited til dark then drove all night into Utah.

 

Utah we had a bad tire, slept in the van at walmart, when they opened we got a new tire. It was a light rain that day, we were able to get almost to Idaho in the rain.

Then the weather cleared up the sun came out .... acted like vapor lock again.

 

We sat till dark. Then we made it into Oregon overnight, by 10:00AM-11:00AM it got warm ..... we hung out in the park all day like bums .... waiting for late afternoon.

We drove all night again and made it to our destination in WA the next morning.

 

We changed the fuel pump & never had the problem again .... We drove it from WA to TX a few times after that.

 

Only saying I have seen first hand how we drove 1/2 way across country with a bad fuel pump.

The OEM pump would not pump fuel when the weather got warm, work all day long in cooler weather. ..... We could hear the electric pump motor working.

Must have been something to do with the rubber diaphragm stretching when it got warm?

 

 

I was referring to the mechanical pump as used on our old Mopars. The in-tank pump may have been a rotary pump which wouldn't have a diaphragm.

[DJK]

Depending on how the electric pump is plumbed in, is it possible the E pump is hitting a restriction through the manual pump? Haven't experienced vapor lock myself, but if  I understand correctly, that occurs when a vehicle is not running and the fuel evaporates from the system due to excessive heat. Asking for a friend. 

[Doug&Deb]

DJK what you’re describing sounds like fuel percolation. That happens when you shut the car off for a short time and it’s hard to restart or it stalls after being restarted. To answer the other questions: my cap is vented and I don’t think the electric pump is causing any restriction. I’ve had it on the car for about 2 years now and this problem just started. 

[D35 Torpedo]

I was also thinking maybe the two pumps are fighting each others. It could be a heat soak thing. The mechanical pump will bypass when the going gets tough, whether it's a restriction on the intake side, or the needle and seat in the carb. Maybe, when it gets hot it can't pull enough. So the float bowl is running low. I was battling a bad tank. When the filter clogged, the pump couldn't pull enough and power would drop off suddenly. How clean is your fuel system? I'd get a rebuild kit, even just to have it. Eventually, you will need it. Try blowing you lines out with compressed air. 

 

Can someone post a pic of how the fuel pump heat shield is mounted? Please, I don't have one. Thanks!

[Plymouthy Adams]

this is my shield in place

[DonaldSmith]

Here's my fuel pump shield:  The front end is secured by a manifold stud and nut. 

 

 

 

[desoto1939]

Doug:  Here isa suggestion. I know back in the 50-60 the lower rad hoses all an internal spring to keep them from collapsing.  Might you be getting this happening on the lower return rubber hose to the radiator.

 

Also did you rebuild your carb?  If you do not have a governor on the carb then the base thick gasket that is need has the four slots cut into the gasket. These slots then will line up to a very small hole.  So check the carb and remove it to make sure you have the proper gasket installed. This is just a Wild Ass guess. What about the sisson choke.?

 

Rich Hartung

Edited April 25, 2023 by desoto1939

[Sam Buchanan]

Way too much thinking going on here......replace the pump.

[OUTFXD]

23 hours ago, Doug&Deb said:

I’m really confused.

Welcome to MY world!

[OUTFXD]

Sounds like my experience.  How is your charging system? 

 

I spent months chasing a "vapor lock"  replaced my entire fuel system. New Fuel pump. New fuel line, New gas tank, I heat shielded the hard lines under the manifold.  I take solace in knowing that everything on Jacquiline is well worn and near breaking anyways. 

 

Things only really cleared up when I replaced the Generator. Oh and the timing.  If you stand infront of the car and look at the engine,  The engine turns clockwise,  Every other engine I have worked on turned ANTI-clockwise.   When I was setting the timing I was accidentally retarding the timing thinking I was advancing it.

 

Just a couple thoughts that MIGHT help you along.

[D35 Torpedo]

So this thing probably shouldn't be sitting on my washing machine then...eh?

[Los_Control]

3 hours ago, Doug&Deb said:

I don’t think the electric pump is causing any restriction. I’ve had it on the car for about 2 years now and this problem just started. 

My long winded story about driving cross country with a bad fuel pump .... things don't always fail in the ways we expect them to ..... they make you scratch your head.

Making it possible your mechanical pump works for awhile, then you need the electric pump to get back home.

Just now, Sam Buchanan said:

Way too much thinking going on here......replace the pump.

Exactly.

One way to justify the cost ..... they are fairly cheap. Today you can find them, couple years from now they may be hard to find.

If it fixes the issue so be it., if not .... you now have a good spare pump you can pack away and carry it with you on road trips in case needed in the future.

 

I think trying the coil is a pretty decent shot in the dark assuming it was bad and overheating .... if it was a ignition issue, the electric pump would have no effect.