Mustang Owners Club Australia Forum
Technical & General Discussion Area => Tech Torque Pre 1973 => Topic started by: Tulls on December 12, 2021, 04:04:46 pm
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Hi, can anyone offer some help with ideas please. I have a 65, 289 with a 4 barrel carb that runs perfect in cool weather. The engine does not overheat, fuel is new and clean as is fuel lines and filter. It has a new fuel pump, insulated fuel lines. It is running the standard alloy spacer block under the carby.
On a hot day (over 35c) I get fuel vapor lock (no fuel in fuel filter next to carby). The engine cuts out and will not start. If I pour a bottle of cool water over the fuel pump, it restarts ok.
Any ideas what I can do to stop this. I was thinking of changing the alloy spacer block with one of those black plastic ??? ones and maybe fitting an electric fuel pump??
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Its certainly vapour lock.
I have a 66 with alloy spacer 4100 autolite carb and only once had vapour lock (41 deg C with a/c on) so something is different. Is your fuel line
running near the exhaust or touching a head?
An electric fuel pump will solve the problem
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Hey Tulls,
Can you move you fuel filter closer to the fuel pump away from heat.
Obviously you’ve checked leakage from the filter to the pump.
How old is your pump, is it feeding back through the pump!
Cheers Phil.
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Thanks for input guys. The fuel pump is new, I replaced it thinking that was the problem but the problem still persists.
I will go with the electric fuel pump as I have done everything else. I have purchased a Holley Micro Mini pump as it is the one suited for my Holley 450 carby.
Should I keep the manual pump plumbed in or remove it altogether....
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Hey Tulls,
Can you post some photos, should not have to go to more expense buying an electric pump.
Can you temporarily turn your filter so the outlet is at the bottom, if the pump is leaking back it should not suck fuel out of the filter. Vapour locks are usually leaks, not so much heat?
If it’s the pump feeding back and your filter is horizontal it should only half empty the filter?
Try loosening them retighten your joints, check for cracks on any flared pipes.
Check your carburettor float valve and fuel float level.
If you’ve still got a full bowl of fuel it should start and run for a while till the pump catches up!
So many scenarios! That new fuel pump may be not good or wrong!
Cheers Phil.
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Hi, can anyone offer some help with ideas please. I have a 65, 289 with a 4 barrel carb that runs perfect in cool weather. The engine does not overheat, fuel is new and clean as is fuel lines and filter. It has a new fuel pump, insulated fuel lines. It is running the standard alloy spacer block under the carby.
On a hot day (over 35c) I get fuel vapor lock (no fuel in fuel filter next to carby). The engine cuts out and will not start. If I pour a bottle of cool water over the fuel pump, it restarts ok.
Any ideas what I can do to stop this. I was thinking of changing the alloy spacer block with one of those black plastic ??? ones and maybe fitting an electric fuel pump??
Similar issue with mine since I had the carby rebuilt. I'm guessing the carby needs adjustment for the car as the company uses a V8 test bed engine to calibrate it which most likely doesn't suit real world operating quirks of the vehicle.
I note you have a new fuel pump, so perhaps that is simply changing the way the car previously operated and it doesn't like it = adjust the carby to suit?
P.S. I'm hardly a mechanic, and am learning that these cars do seem to have individual characters ... women! :lol:
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Thanks again for all the input.
I have done a vacuum leak test on the new fuel pump and it is working fine, no leak back. I even tested the old pump and it too was fine. I removed the fuel filter at one point to see if it made any difference, it did not. I then had the carby overhauled and reset and still have the problem.
I am now 100% sure it is vapour lock which was identified by pouring cool water over the fuel pump when the issue arose. It started pumping fuel straight away after that, and ran good for a while until it got hot again.
All fuel lines are away from the twin exhaust and the manifolds.
All the mechanics I have spoken to agree it is vapour lock, which they say is common on our older cars. But, again it seems only some cars do it............
I am now in the process of insulating the fuel line and will fit the electric fuel pump as well in the coming weeks. I will let you know how it goes.
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Hey Tulls,
Sounds now like it’s worth putting an insulated block under your carburettor!
Cooler fuel anyhow gives you bigger bang!
Cheers Phil
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Just before you go down the road of electric fuel pumps, just check that the fuel tank is venting though the fuel cap.
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Are you running a Holley by any chance? I ran a 600 vac sec for a few years & had similar problems. I removed the original alloy spacer (A-Code car) & fitted a phenolic spacer which helped alot. I eventually ditched the Holley & went back to the original Autolite 4100 & alloy spacer. No more issues.
Evan.
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Does your insulated fuel line run all the way back to the tank? Do you have extractors? If it’s not insulated between tank and fuel pump and is the original line and you are running long tube extractors, have a look at how close the fuel line is next to the collector below the back of the firewall before it turns into the wheel arch. It can get pretty tight and a section of spliced 3/8 coolant hose over the top of the fuel line should do the trick. Using 95 octane fuel also helps too.