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Fuel pump or regulator or something else???

G'day everyone

So, moving the ute on and off the trailer and its getting low on juice, and I mean REAL low (no fuel in the filter)- filled it up on the way home and go to unload it, no joy it wont start ... and hasn't since.

I've got the electric fuel pump jumped straight off the battery at the moment (yes it is on a fuse!) and its making all the right noises and it picked up the fuel (fuel filter is now full). So, check for fuel pressure on the gauge has some but not much (its set real low because of the SUs). Check for spark just in case, chucked the timing light on and its strobing so theres spark at the leads.

Drop the fuel line off the fuel rail, and there is no fuel in the fuel rail, chuck a tin under the line and fire up the fuel pump and its pumping some fuel out not a real lot but should be enough - just. Turn the fuel pump off, and the fuel drains away, no fuel left in the hose ....

Chuck the fuel line back on and fire up the fuel pump again, then crack the fittings at each carb inlet, there is fuel present at each inlet. Still no start. No signs of the carbs flooding back through the return line (I have a clear filter in the return so this can be monitored)

Fuel pump sounds like its going flat chat without any signs of the change in tone it makes when its up to pressure.

So what do you guys reckon - have I burnt the fuel pump somehow / punctured a diaphram running it dry and it cant provide the correct flow / pressure? Regulator stuffed? Blocked needle and seats (X3 its not even coughing though)

Tried a bit of Start Ya Bastard on it and it coughs so I reckon its definately fuel side.

Fuel pump is a Facet and is a diaphram type rather than a rotary type and is old - at least 15 years. Its what I think it is but I thought I'd run it past you guys before grabbing another one.

Cant see a brand on the regulator.

Cheers

Doug

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Hi Doug,
Is it still the original ute tank? Have you had it out during the rebuild? They have a habit of cracking around the pickup joint where the fuel line screws into the side of the tank. If its cracked it will suck air and cause problems especially when the fuel is low (if the fuel is full it covers the crack in the pick up and doesn't cause the problem.
One way to eliminate that from possible causes is to screw a fitting into the tank drain in the bottom and feed the fuel from that point.

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"Tried a bit of Start Ya Bastard on it and it coughs so I reckon its definately fuel side."

With the Pressure set really low, the Pump will work at a continual fast Pace.

I would Cap Prime it, before I tried too much else, to make sure the Problem isn't Ignition ... http://holdenpaedia....

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Paul its full at the moment and still no joy ...

I am using the original tank and standard pick up though, its was running Ok for quite a while until I ran it out - and the fuel filter is full and no sign of air bubbles in it.

T, I am using an electric pump.

I gave it a bit better squirt of start ya bastard tonight and the car actually starts for a short time, definately spark and timing.

The electric pump is only $75 so I chucked a new one in on spec to no avail - so fuel pump is eliminated as the problem ... it does run a lot quieter that the old one though so thats something I guess!

So .... fuel to the fuel rail, and to the fittings to each carb (I just cracked the fittings and had fuel dripping out showing some fuel / pressure there).

I can't see three jammed jets happening at the same time in the triples, but I think I might need to pull the carbs off tomorrow and check out the float bowls.

Cheers

Doug

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"I gave it a bit better squirt of start ya bastard tonight and the car actually starts for a short time, definately spark and timing."

Good. That was my concern.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

gravity feeding the fuel bowls to prime the carbs (assuming you're running SU's) may help, if not check the needle and seats. stale fuel can be a real nuisance in more ways than one.

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If your project doesn't work, look for the part you didn't think was important.

One should forgive one's enemies, but not before they are hanged

mckackie

Was anything replaced during the rebuild?

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Well a little bit of weirdness here ...

Dropped the fuel rail, and blew some air through it, nothing seemed to be in there.

Gave each carb a squirt with the air, and heard fuel / air being forced out of the float bowl vents, so needle and seats not jammed shut.

Connected everything up and hey presto, it starts and runs like a bought one, not rough, just like normal.

Only thing I can think of is the needle and seats on all three are a touch sticky, and the fuel pressure is too low to overcome the friction.

Think I'll crack the fuel pressure up half a psi.

Thanks for your suggestions guys, mckackie maybe the lay off from the rebuild left a bit of residue - strange that it ran no problems for a couple of days though and seemed to be linked to running out of fuel ...

Cheers

Doug

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Glad to hear you got it firing.

Thanks for posting up what you found.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Well since the last post there has been some more problems.

So after it started up I thought I'd found the drama, but when I went to load the car on the trailer it stopped again, with symptoms like it was running out of fuel again!

After much stuffing about the problem turned out to be me shooting myself in the foot ....

Some that have been following my build will have seen that I made up some steel fuel lines, and also steel lines from the float bowl vent - these nasty buggers are sitting right above the exhaust and alternator on the front carby, and is where fuel pours out if you get a float sinking. Having had this happen to me, I decided to run a return line from the float bowl vents back to the fuel tank.

This created the problem!!!

The problem was that the return line created a closed fuel system, so that when some of the fuel in the tank was used, it created a suction force back up the return line, because there is nowhere for the air to get in - this must not have been a problem originally (such as creating a strong enough vacumn to collapse the tank!) as there was no air vent to the tank, but it didn't affect the carbies because there was no connection.

There must have been enough suction force back up the return line to draw the air out of the float chamber and sucked the floats up causing the needle and seats to close! I proved this as the fault as I got the car started again as before by squirting a little air down the fuel line (which obviously overcame the suction force) and when the symptoms repeated I just disconnected the return line, and away she went, with no further problems.

When I initially started the car, with very little fuel in the tank, there was plenty of air space in the tank so the fuel being used must not have had the same effect due to the larger volume of air.

Simple fix in the end (aren't they always when you know the answer!) with the addition of an air vent.

And the lesson? - SUs need the float bowl vents to be open to the atmosphere.

Well, I didn't know that.

Cheers

Doug.

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