Warmer Weather Woes

[cplynn]

I was driving my Bronco around this afternoon running errands--about 15 miles total--and after my last errand my Bronco would not stay started. After investigating a little it was evident that my high pressure fuel pump was running, but the low pressure pump was not. Engine temp was at about 210. All the wiring was intact. After waiting about 30 - 45 minutes the low pressure pump kicked back on and everything was fine; I was able to get home. I have a Carter low pressure pump. Has anyone seen this or experienced this before?

This is the first summer I've been running my Bronco since completing the EFI conversion last summer. Another thing I noticed is it seems my gas tank is building up a lot of pressure, particularly when it's hot outside. Got gas today (that was my last errand) and when taking the gas cap off it made a pretty significant "HSSSSSS". Venting issue?

[Gunnibronco]

I don't think the gas tank venting would cause the pump to shut off. But I'd make sure the tanks are vented right. Mine weren't after installing my new high capacity tank. I didn't have any fuel problems, but had significant pressure/vacuum build up- after driving long distances, high temps, transferring fuel from my aux tank to my main. I ran simple (not EPA compliant in any way) vents to each tank just to eliminate the potential problems. The stock gas caps do some venting, but not nearly enough.

[Jesus_man]

My guess is the pump relay. I had/have one that cuts out if it gets wet. Took me a long time to figure that one out. Maybe find yours and try to relocate it away from the heat source. Oddly enough, that relay also likes to be mounted in a vertical position. If it's laying on it's side it will cut out when hot too.

[landshark]

the pressure might be building up and killing the low pressure pump.. or the low pressure pump might be on its way out.. either way you need to fix the venting as its not doing your pumps any good fighting the pressure I would think.

[B.O.B.]

Not to hijack but what is the best way to vent your tank. I have a vented cap but can here it hiss after driving. Aftermarket 23 gallon.

[Gunnibronco]

I think this is the easiest way:
http://www.tanksinc.com/index.cfm/page/ ... /prd98.htm

'T' it into the tank, and mount the vent higher than the fuel filler.

You'll smell gas when the tank is full & weather is hot, or if its parked in a garage. If you don't want to smell fuel, you must route it through a charcoal cannister. Someone else can elaborate on that.

[Viperwolf1]

Christian, it does sound like a venting problem. If it happens again pull the cap off and see if it runs good afterwards.

Bobby, I like the venting system on the '70 and later Broncos. '76-'77 had a simpler version that works well. Pre '70 Broncos won't have vent tubes in the stock tanks.

[cplynn]

So, Viper, do you think the venting issue and problem with the low pressure fuel pump are related?

[Viperwolf1]

So, Viper, do you think the venting issue and problem with the low pressure fuel pump are related?

If the tank doesn't vent it becomes difficult or impossible to pump fuel from it when a vacuum is created. When fuel volume drops air needs to go in to replace that volume.