s14a bent cam massively over fueling

[dougalson]

hi,
first post on here but a bit stumped, as title its a s14a which ive had welded up and resprayed, engine was pulled for a clean up inc painting inlet manifold, rocker cover, new genuine oil pump and water pump, new belts, new clutch and flywheel and then refitted , since the refit i cant seen to stop her massively over fueling, seems to fire every time but then want to die instantly, if i add any throttle kills it even sooner, when warm i can get to about 2k before she start chocking again , was a perfect running 302 bhp engine the day i stripped it, its a horsham stage 1a , no bov , no abs, no aircon , plugs are new, new water temp sensor, tried a known maff which made no difference, tried new lamba sensor which again made no difference, no codes from consult plug, brand new 255 walbro fuel pump, new z32 fuel filter, have also changed fuel pressure regulator which again made no difference , check timing and she on +15, have reset caz timing, spent hours looking for boost leaks but cant see any.....

anyone who has any ideas would be greatly appreciated as not sure which way to go next as dont really want to wash boars out and standing in garage with it running (just) kills my eyes

many thanks

[Hugh Janus]

sometimes a simple look ( or even extensive) over won't reveal vacuum leaks, best get it pressure tested (not smoke)

[dougalson]

Yeah tried the boost pressure test but couldn’t see anything , managed to fit a fuel pressure gauge today and on priming it hits 2.9 bar but as soon as it starts the pressure drops too about half of that ! It’s a brand new walbro 255 so I’m thinking it’s the voltage to the pump dropping when started as I’ve seen a few people having to hardwire the pump to keep its 12 volts , does this sound about right ?


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[Chriscooke]

Increased fuel pressure would make it richer surely.

How do you know it’s over fueling? Sounds like another issue to me. Faulty sensor or something not plugged in perhaps. Or a decent boost leak as mentioned.

[dougalson]

Yeah I thought it was over fueling but now I’ve fitted a fuel pressure gauge and it drops to zero when I rev it so I’m now thinking it’s the complete opposite it’s running out of fuel when it actually wants more ….


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[Mike41288]

If your fuel pump isn't getting enough power, it would cause engine to run lean not rich. If I remember correctly, the base fuel pressure is around 3 bar (just with fuel pump primed, no start and no vacuum hose attached) and it should increase as the boost increases.
Are you sure it's a proper Walbro fuel pump? I know there are fakes floating around on ebay etc that have killed peoples engines.
The fuel pump hardwire is basically a relay that feeds the fuel pump power straight from the battery via a larger gauge wire than standard which is more capable of dealing with the power demands of a larger pump. The standard fuel pump wiring feed into the relay and acts as the trigger to switch the power to the fuel pump on.

[dougalson]

I do hope the pump is real , otherwise I’ve been robbed of £75 , I did take a walbro out and fit a walbro in and they were same , although this probably means I didn’t need a new one anyway, pump does make 2.9 bar on priming just when it starts the pressure drops half and if I rev it it goes to zero


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[dougalson]

Guys back to being stumped again , thought car was not giving the fuel pump enough voltage but had the multi meter on it and she getting 12 volts when running , so I’m getting 20psi on idle but soon as I rev it it’s going to zero and dying , have swapped fpr for another and still the same ?? She is pulling -15 psi of vacuum and I do remember before she used to pull -20 psi before the strip down ? I would assume a vacuum/boost leak but can’t find any


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[piman2k]

If you're getting no codes and it's not running it suggests something mechanical.

The FPR going to zero, I'm not a mechanic, but does the polarity of the fuel pump wiring matter? Could it be back to front?

What about the IACV?

[dougalson]

The iacv I have had off and cleaned but could do with trying another , ground wise I will be putting another to the bottom of the block to chassis tonight , I shouldn’t think I have got the wires wrong as I get 2.9 on priming but am testing pump voltage when revved tonight to make sure it’s staying at 12 , probably be doing the hardwire just to be safe


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[piman2k]

But voltage goes across terminals, it's not directional, current is. If the motor has polarity then connecting the wrong way would make the pump go the wrong way.

[Chriscooke]

Seen the pipe that goes from the fuel pump to the top hat split and spray the fuel back in to the tank resulting in low fuel pressure. What pressure regulator do you have?

[dougalson]

Just a standard one , have swapped it for another one but still the same , in the fsm it’s says that fuel pressure should decrease when vacuum increases ? When I rev it loses all pressure ?


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[dougalson]

Would the car start at all if the pump was wired round the wrong way tho


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[Mike41288]

Revving without load wont generate any positive pressure, the FPR will just see 0psi/bar whilst revving. Idle should be around 0.7 bar of vacuum.
How long does the fuel pump prime for when you first turn on ignition?
How much fuel do you have in the tank?
Did you fit the original filter sock thing on the bottom of the pump or what was supplied?
Have you tried taking the fuel feed from the rail off, extending the line into a bucket or container and turning ignition on to check flow from the pump through the lines?
Have you checked the vacuum line from the plenum to the FPR for any splits or damage?

[Mike41288]

Seen the pipe that goes from the fuel pump to the top hat split and spray the fuel back in to the tank resulting in low fuel pressure. What pressure regulator do you have?

This is also a possibility, same thing can happen if a clamp isn't tight when installed. Defo something to investigate. If voltage to the pump is constant and it's building any pressure, the pump is most likely doing it's job fine, it's something to do with what's in between the pump and the injectors, in my opinion.

[dougalson]

Revving without load wont generate any positive pressure, the FPR will just see 0psi/bar whilst revving. Idle should be around 0.7 bar of vacuum.
How long does the fuel pump prime for when you first turn on ignition?
How much fuel do you have in the tank?
Did you fit the original filter sock thing on the bottom of the pump or what was supplied?
Have you tried taking the fuel feed from the rail off, extending the line into a bucket or container and turning ignition on to check flow from the pump through the lines?
Have you checked the vacuum line from the plenum to the FPR for any splits or damage?

My boost gauge is showing -15 at idle at the moment but before the strip down I remember her pulling -20 , pump primes like normal (about 3 seconds) , tank is fairly low but above red , I did fit the sock to the pump that was supplied which was smaller than the old one , car was still doing this with old pump fitted too , haven’t checked to flow out the feed so I’ll do that, vacuum line is new to fpr as was red and wanted black


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[dougalson]

This is also a possibility, same thing can happen if a clamp isn't tight when installed. Defo something to investigate. If voltage to the pump is constant and it's building any pressure, the pump is most likely doing it's job fine, it's something to do with what's in between the pump and the injectors, in my opinion.

I have no fuel leaks that I can see of , multi meter reads 11.98 ish at the pump when at idle and small revs


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[Mike41288]

I have no fuel leaks that I can see of , multi meter reads 11.98 ish at the pump when at idle and small revs


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It's the hose inside the tank that connects the pump to the top hat, thats what we are talking about

[dougalson]

It's the hose inside the tank that connects the pump to the top hat, thats what we are talking about

Right ok I’ll pull the pump in a bit and have a look , cheers guys


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