Vapor lock?

Peter B

Peter B

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Last week my beautifully restored 1973 Fjord 3.0 CS got the nod in the rotation. I drove it on a very hot day in south Florida with the AC on to a friends house and it sat in the sun for a hour. When I got to leave it fired up, I backed out, and drove off…but only about 100 yards and the car stopped. The electrically systems were workng, but the car would not move. I turned off, turned back on but car wouldn’t engage. Thought I was out of gas but the gage said otherwise. The car was flat bedded back to my office (closest spot) and I left it over night. Next morning it coughed twice, then fired up and runs great. Any ideas? Ethanol boiling?
 
Yeah, give us some more detail. Do you have the stock Zeniths, with the stock fuel pump? Or is the car modified? Are you up to date on your fuel filter changes?

When you say the electrical systems were working, do you mean the starter functioned? If so, did your car give any sign of wanting to fire up?
 
I have fought a similar condition for a few years. I installed the electric fuel pump which does overcome the condition which was happening after a stop (heat soak). Recently, I removed the fuel filter under the hood and put a small filter in the trunk. I also replaced the rubber hose from the steel line to the fuel pump with known good hose. We have driven it a few times with no issues but it hasn't hit 100 yet here in the Hotlanta area.
 
Coupes are notorious for not ever having vapor lock?
 
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My (injected) CSL did this twice. Fully rebuilt everything.
First time 10min after leaving mechanic for first drive. Car coughed then died. Turned out the temporary fuel cap didn't have a breather hole and it created a vacuum. Pulled the cp and cranked a bit and off we went.

Second time 45min into a run and the car coughed, lost power over around 200m and died on the highway (right outside a kids prison) - not making this shit up..
Car fired back up after 5 min, still a bit of a mystery why this happened. Car had been stood for a while, so I'm thinking an air lock in the fuel line or something like that.
 
i hope you never tell your daughter that there are kids prisons…..
‍:(
 
Wait a minute….wait a minute…

you don’t need a vented gas cap on a coupe….

The tank is vented at the filler neck….





IMG_1954.jpeg
 
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And- if your vent hose were blocked, it will take a lot longer than 10 minutes of running to create enough vacuum to stop a Csl fuel pump from working.

A lot more likely that it’s the fuel pickup not able to handle the fuel going backwards in the system because you are in the Southern Hemisphere…..
 
BMW gas cap are labeled “ohne luftung” - without vent..







IMG_1955.jpeg
 
sfdon said:
And- if your vent hose were blocked, it will take a lot longer than 10 minutes of running to create enough vacuum to stop a Csl fuel pump from working.

A lot more likely that it’s the fuel pickup not able to handle the fuel going backwards in the system because you are in the Southern Hemisphere…..
Click to expand...

In order of offence :)

Yes - Lola knows about kids prisons - it where kids who leave food in my cars go
Good point on the pick up, not sure what was going on then - perhaps it was just an air lock as part of running in as was first time car was on the road?
 
Peter B said:
Last week my beautifully restored 1973 Fjord 3.0 CS got the nod in the rotation. I drove it on a very hot day in south Florida with the AC on to a friends house and it sat in the sun for a hour. When I got to leave it fired up, I backed out, and drove off…but only about 100 yards and the car stopped. The electrically systems were workng, but the car would not move. I turned off, turned back on but car wouldn’t engage. Thought I was out of gas but the gage said otherwise. The car was flat bedded back to my office (closest spot) and I left it over night. Next morning it coughed twice, then fired up and runs great. Any ideas? Ethanol boiling?
Click to expand...
https://e9coupe.com/forum/threads/vapor-lock-question.19485/
https://e9coupe.com/forum/threads/vapor-lock-electric-fuel-pump.34361/
 
I recently replaced my fuel filter and fuel pump. I started getting vapor lock. I was able to drive it home by getting a bottled water and spraying the water onto the two new parts to cool them down. It ended up that the new fuel pump was the problem. When I switched back to the old one everything was fine. Yeah, I was switching out a working old fuel pump for a new one.
 
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