Fuel Starvation

[Tim Smith]

I'd be too afraid of cracking the exhaust header to run water over a hot motor. Guess I shouldn't be...

[greenmeanie]

It's pretty much the same as hitting a deep puddle so I don't worry.

[gudjeon]

I was frustrated with the mechanical system and diagnosed it down to fuel starvation. A new faulty replacement pump only added to this. I opted for an electrical pump and used a recirculating fuel system. Added one extra line to the system but no vapour lock and no more difficult hot start up. It's not pretty, but it works. Late 80's Chrysler spec fuel filter and fabrication of return fitting onto tank. (note) the air intake elbow is fabricated because is needs low clearance for the 2.25L in my ser1.



This is what I used the old pump for once I got to the bottom of the problem.

[Leslie]

Have you verified that your pump is up-to-snuff? Checked its rate of flow into a bucket?

If your fuel pump checks out, and your lines are clean, along w/ the pickup tube, and you're sure you don't have crud in the tank getting pulled over to block off the flow, then in that case, vapor lock is the suspect, IMO.... FWIW.....

[daveb]

*total* long shot but is the sediment bowl perhaps a bit on the loose side of things and when she warms up it allows air in?

oh and did this happen before changing the fuel pump or did it start after?

and gudjeon there were a few LRO's a number of years ago that had some sediment bowl shot glasses engraved with LR club logos. Wish I had one...

I just changed out the fuel pump last weekend and it came with a new glass bowl. Vapor lock sounds like it could be the issue after some reading. Over at LRO there are a couple good posts on it from a 109 in Dubai.

Has anyone that lives in a hot climate insulated their fuel lines? I would think this would help. Any suggestions on a brand of tubing insulation?

[jp-]

Gudjeon,

If you use a low psi generic electric pump (3 to 7 psi) there is no need at all for a complex return system, as the carb needle valve can easily handle the pressure. Fuel return systems are generally used only in high power carb applications where the carb may need a great deal more fuel at high rpm, or in EFI applications.

[gudjeon]

Howdy jp,

That is what I first thought when I went to the electric pump and I hooked it up inline. I purchased a low pressure pump from NAPA that was set up for carburator systems. It turns out that it flooded my engine silly when it was shut off hot. The fuel pump did not release pressure once shut off. This paired with the elastic nature of the fuel line, enabled an unwanted amount of fuel to feed the carb when shut off hot. I went to a return system and no more problems. Vapour lock disappeared altogether and now my fuel is constantly filtered as a bonus.

[jp-]

Either the pump has just a little too much pressure, the needle valve has problems, or the float may not be working as well as it should, because I have had no such trouble on vehicles that I have put electric pumps on.

The fuel being filtered is nice though.

EDIT: It's also possible that the fuel pump has an anti-drainback mechanism on shutoff.

[gudjeon]

I suspect the drain back was the issue in my case. I installed those little universal pumps in the past and never had an issue either. The main thing is it works