Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.
I have been fighting this issue for a couple of months as well. I believe the vapor lock symptoms with the Mopar MPI Hesco setup is, at least, partially due to the quality of gasoline we have these days.
First time it happened to me my CJ7 stalled several times, on a 95 plus degree F day, before I could get home--had to let it cool each time before I could get it to start. As a result, I reran the fuel line from the driver's to the passenger side, under the radiator to the rail to get the line away from the exhaust system. Put thermal wrap on lines in engine compartment, dropped the tank and replaced lines and roll over valves. Reran the charcoal canister vapor line. And moved the pump and regulator to frame (do not off road my CJ7 ) by the Transfer Case (based on comment by Torxhead on his TBI setup).
After doing this, on the next outing, I only had one instance of the vapor lock like symptom--after a whole day of riding (over 100 degrees F) with the air conditioner on. Still not satisfied, I made a shroud for the electric fan on the radiator to redirect air flow off of the rail/intake manifold. After doing some research on other sites of retrofitting EFI to older engines I am in the process of adding a low pressure "lift" pump and a fuel accumulator. Have also added a fuel cooler on the outside of the frame on the passenger side to cool the return fuel from the regulator to the tank. Probably overkill, but I hate being stranded on the road.
Picts of the shroud, fuel cooler and accumulator attached. Also, 2 pdf files on EFI.
You must register or login to view hidden content on this page.
I'm having the same trouble Tin Medic. I have the MOPAR fuel injection conversion on my 1974 CJ6 . Probably did it 10 years ago. I'm on my third "Performance" external fuel pump, and it's going bad now. Driving on a hot day with warm fuel seems to make it worse.
The warning sign is the very audible noise the pump starts making plus the pump being hot to the touch. Shortly after the engine starts stumbling as air gets into the injectors soon followed by complete shutdown.
I'm pretty fed up with the external pump and joined this forum today with hopes someone out there has a remedy.
I was thinking a submersible pump may be the answer, which should keep the pump cooler and air out of the lines???
The external fuel pump does have its drawbacks. It requires that the fuel lines be clean an free flowing, this also requires a vented gas tank. In your case there might be an issue with the fuel pickup sock if you have one or a clogged fuel filter. It does sound like the is a problem with the fuel getting to the pump.
My apologies to Tin Medic--do not mean to highjack this thread but wanted to add followup. I put the Carter low pressure fuel pump in (have it on its own relay) and the fuel accumulator (see previous post above). Right now all of this is mounted on the passenger side frame until I can move things to a more permanent location.
I have had my CJ7 out twice since this modification on all day drives, with air conditioner running and have had no further "vapor lock" incidents. These drives were done on some of the hottest days that we have had in Arkansas this summer.
Of course an in tank pump is the ultimate solution. Lee at HESCO suggested another option if you do not want to modify your tank or put in an aftermarket tank or YJ tank. This option uses a low pressure fuel pump like the Carter, a 1 gallon sump tank, in which you can place the high pressure pump (to keep the pump cool by sitting in the fuel in the sump tank). If interested, I would think he would be willing to help you. Contact him at Hesco Inc. - High Performance Engine Service
Last edited:
Register now
You must register or login to view hidden content on this page.
