Zero fuel pressure cause?

[jhelgesen]

I'm trying to track down my low to zero fuel pressure issue before my next track event. Here are the details.

3.0 converted from CIS to webber 46's. Pierburg CIS fuel pump, PMO pressure regulator, set at 4lbs, stock tank. -6 lines running front to rear, in and out.

Car was idle on and off for 2 years. Started weekly, but drained tank and ran out carbs in last few months.

Several weeks ago, tank got several gallons in it, carbs checked clear when opened. Jets and such clean.

This weekend, went to track event. Filled tank completely.

Car ran fine first session, no issues, but not stressed 100%.

Noticed fuel smell and dirt on side of car, found vent line was not connected to filler neck.

Temporarily ran a line from the vent, down to bottom of car.

Ran next session, but got fuel starvation in turns starting about 10 min into session.

Brought car in, found vent line kinked, then found correct line from tank and reconnected. Fuel pressure running 3lbs, adjusted pressure back to 4.

Ran next few sessions with same results, 10 min, then starvation....

Next day, flushed out fuel filter (several years old) and got lovely red residue out. (couldn't locate spare filter)

Next session, same result. Left car running in pits after run, saw zero fuel pressure on gauge on regulator.

Located spare filter, changed out.

Ran last session, same result, same zero pressure on gauge.

Noticed old line to tank has kink also.

Sooooooo, I have several things to check now.

1. Unkink line, put catch can/charcoal canister back in line

2. Drain and flush tank, check and replace in tank filter.

3. pull and clean regulator

4. replace fuel pump


Am I missing anything? Suggestions?

[DW SD]

Are you running a return line? Maybe your fuel is suffering from vapor lock (boiling). I assume this means there is a return line though: "-6 lines running front to rear, in and out."

Where is the filter? Do you have a pre-filter before the fuel pump?

what kind of venting do you have on the fuel tank?

Doug

[jhelgesen]

The system is a converted CIS system with a return line. Recirculating fuel system from the PMO fuel regulator. Venting is done with the line from the top of the tank going to the side of the filler neck.

Filter is in the back of the car, mounted to the old CIS accumulator position, pump is on the front cross member, no pre filter.

[DW SD]

Are you running a return line?

last time you had zero pressure, was the pump running? Could you hear it? Maybe the pump is overheating.

Doug

[jhelgesen]

Yes, has a return line.

Can't hear the pump over the engine, would have to check that.

The second we turned the car off, then back on, pressure was back up.

[DW SD]

John,
I'm sorry about the second question about return line. I read your initial reply too quickly. Will it die after 10 minutes driving on the street?
I wouldn't be surprised if it is the pump. How is the pump turned on? Is there a relay? Could that relay be overheating?
How old is the filter? please forgive me if you already detailed this

Doug

[jhelgesen]

Can't really drive the car on the street, pretty much open exhaust.

It never dies, just cuts out trying to go over about 4k in hard acceleration. Feather the pedal, back off a bit, and she keeps going.

Pump has a relay, but is a standard black one. Thought of that this afternoon. Need to put in a red fuel pump specific relay.

First filter was 5 years old, second filter was new.

[DW SD]

how about the pickup screen in the tank, or is it a fuel cell? Could that be an issue?

[jhelgesen]

Had not gotten to the screen yet, have to get it on the lift and drain the tank. Peeking in the tank sender, inside looked clean, but never know without pulling it.

[JP911]

Had a very similar problem caused by very similar circumstances last year. Stuff was dislodged from the tank which clogged the pre-pump filter, causing starvation on-track. Turned out some of the crap had made it all the way into the carbs, partially clogging the jets. The pressure gauge was also polluted, which caused funky readings. Replacing the filter elements and cleaning the carbs and gauge were a start, but I also ended up with a new gas tank. If you didn't have a filter before the pump you should also give it a good cleaning.

Good luck!

[jhelgesen]

Update:

Pulled the tank and cleaned, small amount of rust cleaned out and treated the inside (just metal ready)

Pulled the fuel pump and found a fur ball looking substance (dirt and rust flakes) balled up in the pre filter in the end of the fuel pump. Removed and cleaned.

Reinstalled everything and fired her up

Fuel pressure was high, so I backed down to 4lbs

When warm, rev'ed throttle and pressure went to 6 lbs and stayed there. Turned car off, did same, started at 4lbs, rev'ed, then went to 6 and stayed...... grrrrrrr

Adjusted regulator all the way out, won't go under 6 lbs.

Pulled gauge off regulator, cleaned, reading stayed the same.



Next I'll pull the valved out of the regulator and see if htere is crap in it. Can't get fuel pressure under 6lbs now.

[jhelgesen]

Pulled the regulator and found nothing in it.

Attached a hose to the return line and gave it a puff, couldn't. Blew hard and got some air in, then heard a hissing from the tank. I must have partially plugged the return line when it was cleaned, so I'll drain the tank tomorrow and try to clean out the return line.

[jhelgesen]

Cleaned the line and the pressure was back down with the pump on. Adjusted back to 4 lbs, started the car, pressure rose to 5 lbs, so I backed it down to 4 while running. Have to fix a brake issue, then I can drive around the block to see what the pressure does.

[jhelgesen]

Issue solved.

When I pulled the fuel pump to check the tank, found a fur ball of crap in the strainer in front of the fuel pump. Ran 3 days at VIR with no fuel issue..... New item to add to my annual prep list, check fuel pump screen.

[DW SD]

Originally Posted by DW SD

how about the pickup screen in the tank, or is it a fuel cell? Could that be an issue?

Nice, only my fourteenth guess !!

Doug