Hey Guys! I'll try to make this brief.

Background: The car was pulled off the road for winter 2011. About 40L in the gas tank, I added a stabilizer and half a liter of methanol. Brought home in May 2012, engine seized. Spun rod bearing from the cap being on backwards. Engine out, rebuilt with a .020 bore, same compression ratio. The engine was reassembled in fall 2012, primed with the oil pump and the cylinders got a quick oil bath to prevent rust. Engine back in a couple months ago. First start today.

Fuel system: Walbro 255 with rewire, hardline to Russel filter, braided stainless from filter to Magnus fuel rail to Aeromotive FPR to return hardline. PTE 780CC injectors. Everything at the engine was disassembled and cleaned, but the only thing replaced was the fuel pump's inline fuse (the old one broke on the way out). AEM EMS for a brain.

Today: Primed the engine with a hand pump and a tube stuck into the filter housing. Put a bottle of Lucas octane booster in the tank to help the 2 year old fuel. Pushed it into the driveway to fire it up. It took awhile to be able to hold enough fuel pressure to run (which I figured was just air). Eventually it fired up but would not stay running without help at the gas pedal. Fuel pressure at idle was over 50psi, wideband was stuck on 10.0, though it was still burning through a decent amount of oil. I pulled the vacuum line off the regulator and plugged it, which changed nothing.

My conclusions: Something's fucked! When the fuel pump primes (yes, my fuel pump primes..), the fuel pressure goes right to 43.5psi and holds. Cranking is when it seems to jump up. It seems weird to me that after all the work I did, the FPR would sh!t the bed even though I didn't touch it, and it worked fine before. That and it seems to have its base pressure set. I'm breaking for dinner but I'm at a loss. For those of you who made it through the whole post... any ideas?!

I can't comment on the AEM EMS, but just a couple things here.
Lets go through a list of things with a simple Y/N answer.
Plugs ok? (condition, gap, etc)
Wires on correct cylinders?
Injectors properly compensated for?
I have no idea why you'd be pushing 50psi of fuel pressure unless something is messed with the lines on the AFPR. You should be running ~30psi at idle with 20inhg of vac. (judging from my numbers)
Boost leaks?

Interesting issue though.

I know when I was running link, I forgot to simulate narrow band operation which caused a no start. Would peg at 10 for AFR, run for 5 seconds then putt and die.

AFPR doesn't have wiring

I recall reading a post somewhere on Link Forums from the Link guys saying that your idle fuel pressure should be approximately equal to this formula --> IFP = BFP (= 43.5) - (Idle Vacuum/2).

So if vacuum is 20, IFP should be no higher than around 33.5, possibly lower.

Have you made sure all your settings look good? Make a list of what items have been changed since you took her off the road and which, if any, of those items would possibly affect fuel pressure, AFR, etc. Have you changed your EMS files whatsoever?

Lines. I was thinking about lines. Fixed now

Fuel pressure on a 2G should be 43psi with the car running and vacuum line removed. If you set your fuel pressure with the car off, you've not compensated for the drop in pressure due to the injectors opening/closing.

If your car won't stay running unless you have your foot on the pedal I'd say you have either an injector compensation or airflow calculation wrong.

Great ideas guys, I appreciate the input. Keep it coming!

The tune on the car has not been changed. It was originally tuned by Marco and nothing in the fuel system has been changed since.

Johnny, for your list:
-New plugs, double checked the gap
-As far as I know the wires are hooked up properly. I have a 6 bolt with 1g coil packs and igniter, and have kept the same wire configuration as to when I got the car, which was double checked against the Haynes manual
-Injectors should be properly compensated for on the existing tune
-Intake seems to be leak-free. I managed to build 30psi of pressure in it with my piece of sh!t BLT. It didn't hold the 30psi, because my POS BLT leaks. It's on the to do list...

Pulling the vacuum line off of the pressure regulator seemed to make it harder for the engine to start and get itself running. So even though it's wonky, it DOES appear to be trying to compensate for it's vacuum signal.

My dad (who's been with me all day) offered a simple solution: a plugged up fuel return line, acting as an extra restriction that the FPR can't compensate for.

I really didn't muck around with the fuel system, as it's never given my problems. Even the usual issue with Aeromotive FPRs losing pressure right after shutdown has never showed up. She's still pegged at 43.5 now, after 2 hours of not being touched.

If you pinch your return line at the rubber section. You pressure should rise if it doesnt you dad may just be correct.

It may be the coolant temp sensor.






lol.




Actually Id start by running an extra bit of line off your return line and into a bucket and purging all the 2 year old gas out of the tank. And if you can purgethe entire fuel line then you will see if there are any clogs. I did this on my 2g with 2 year old gas and it started right up with some fresh high octane gasoline!

The more I think about all the symptoms, the more I'm confident that there is additional restriction after the rail. Which leaves only a couple options; I may just owe the old man a beer on this one







First thing on the to do list for tomorrow night!

Few questions, sorry if they're a bit stupid:

Can an FPR seize up if left sitting for an extended period of time? I've never actually opened one up; I'll probably be able to find the answer with some searching..

Also, since I'm AEM-illiterate, I can make my fuel pump run by pulling off the relay and jumping the connector, right? I suppose I'll need to slap some flat terminals on the end of some spare wire.

If the key is out (and therefore ECU is off) the injectors will all stay closed, correct? Just making sure I don't do something stupid because I assumed I was right

The 2g has a fuel pump wire on the fire wall by the battery. jump 12v to that connector and the pump will run without the key. The injectors will stay closed.. I thoight Aem had a manual fuel pump control.

the fpr is sorta like a wastegate or bov. spring loaded And the vacuum or boost pushes or pulls a diaphram that opens or closes a valve. It wont sieze But it does go bad.

The valve could sieze are you able to adjust pressure if you try?
No the injectors will stay closed with the key off aslong as you dont a leaky one.
You can jump the pump either at the relay or at the connector like Jay said. I have no clue about AEM.
Flushing out that old fuel is probably the best idea.
If you a compress blow some air thru the return line see if it fliwd with the gas off of course.

I'm going to look into controlling the fuel pump with AEM tomorrow while I'm at work. Just getting backup plans ready

Thanks for the tip on the connector on the firewall, and the info about FPRs!

I was thinking of running the pump first to see what comes out the return, and then going to compressed air if I think something's afoul.

If I don't get any tangible results there I'll go to playing with the FPR. One way or another, I agree that the old fuel won't help when there's a fuel system problem. That sh!t's gotta go!

Remember that 140psi from a air compressor is alot more powerfull then the 50psi of fuel. You fuel system may not handle it. Keep it regulated.

If the line is clogged. then I would start with a new filter.. then fpr.. then replace the lines. But I think something is not set up right. Or got bumped.

Then one would ask the question, "How did the line get clogged?!"
I'd recommend opening up your AFPR for a closer inspection and checking your filter before messing about with your line.
But either way, interested to see what the issue is.


Time for a bonfire!

I would just be taking the AFPR and opening it up and checking it.

Did you confirm that you are getting vacuum to that line that is on the AFPR?

I set my AFPR with the car off so I don't think it's a huge issue.

Well, I want to purge out the old gas, so I'll likely be leaving the system intact until I run at least 30L through. I don't think the line is BLOCKED, just restricted. Although I would be more inclined to think that the FPR didn't like sitting, doing nothing for two years.

When the pump primes, pressure shoots up to like 55psi and then backs off to 43.5psi before cranking. So I think the FPR knows what pressure to get to and is able to get it there, but there's something slowing the fuel's return to the tank. With the pump running constantly, the FPR is doing its best but can't drop the pressure low enough.

Once the old fuel gets flushed through, I'll pull apart the FPR and dig the filter out. I think I remember opening the filter and cleaning the element, but that was back before Christmas.

Well whatevery you are doing you better hurry up the KW Meet is in 10 days!

I didn't have time to get at her tonight, but I've got all weekend free to get this mitsubitchy running

Okay, I've got my AFPR out and apart. The spring has some corrosion and can't be compressed very far by hand, but everything else appears to be fine.

How will I know if this thing is causing my problems?

I don't know forsure but if the spring wont compress it wont lift seat or valve which would cause higher fuel pressure

Well I really don't know what else it could be at this point... if everything after the regulator is clean and clear, and the fuel pressure is wonky at a constant RPM even with the vacuum line off, I feel like it would have the be the regulator that's causing the problem..

And since the diaphragm seems fine, I have to think there's a problem with the spring.


Thinking about it from a different angle though: what if it's just the gauge that's fucked? Would the fact that the engine's burning off some oil and assembly lube be enough to keep the wideband buried on rich?

Do you have a cat? Do you have any bluey smoke out the tail pipe? I would asume if you cant change the fuel manually with the set screw that there is somethin wrong with the spring.

No cat, and the smoke is a lot more grey than blue. Everything appears to me as if it's running really rich (because of way too much fuel pressure). But I've checked everything at the regulator back and can't see any obvious issues.

My Dad's new suggestion is that the tank's ability to vent is compromised, and excess pressure in the tank is what's slowing the return. That really doesn't seem feasible to me, but once I get everything back together and fire it up, if the problem persists I'll try leaving the gas cap off.

Gonna shoot down to Ziggy in the morning and grab some parts just in case. Performance parts available on the Sunday of a long weekend at great prices...the man is a saint!

You will still change the pressure with the set screw if the spring is for some reason .. not working the way it should. Altho I think the spring would have to be heated up alot... or really old to ever not hold a steady pressure. Aftermarket fuel regulators may leak..but they dont normally wear out.
I still thinkyou should purge the old stuff first and start from there. Old gas wont burn and will give you a rich reading... cause its not burning. The car may start but as soon as tries to idle It cant find stoich with weak gas.

Jesus if i knew he was open i would of grabbed new fuel lines aswell. Oh well winter project now.

I dont think fuel thank venting is your issue but no harm in checking. You could run seperate return into a jerrycan see if that helps. But my guess is the regulator

Well the regulator is about 8 years old I believe... and it has spent the last 2 sitting doing nothing, often without any fuel in it.

I have purged most of the old stuff out and have been filling jerry cans with some fresh 94 octane. I agree the old fuel didn't help, but old fuel won't cause fuel pressure to be all over the place.



I'm not sure if he's really open or just doing me a favour because I asked really nicely and am a pain in the ass like that

I figured taking the cap off would act as a vent, avoiding the need for a separate return. My guess is also the regulator at this point.

The regulator spring in my 1g sat dry for 4;years and its 20 years old and works fine. But you never know. Do you have a stock you can replace it with?

Unfortunately not, but the 255 with rewire would overrun a stock regulator anyway so I'd still have too much fuel pressure..

Of course there will be some that last longer without a problem, but my point was that the FPR isn't new

And my hands still smell like gas because of it...

Ah yes, a big "thank you" to Salomon who helped me keep about 20L of fuel away from the environment (and into the tank of my shitbox Rio!)

So, a new AFPR from Ziggy changed nothing. Not exactly the cheapest way to rule it out, but I knew it was a gamble..

With the FPR cranked down to 28 base pressure, it fluctuates between 30 and 40 psi while running with the vacuum line detached. When it was at 43.5 base pressure, it was spiking in the high 40s-low 50s (vacuum line detached).

The symptoms are seriously baffling...

where is the vacuum source?

Bottom of the manifold, split to the boost gauge (same as it was before). But it's the behaviour of the fuel pressure with the line disconnect that is truly confusing me...

What happens if you pinch off the return?

I'll have to try again tomorrow; there are too many families around. I waited for them to go inside to eat earlier and then had at it. I'm not sure I'll go back at it tonight, but tomorrow I'll try running the pump with the car off and pinch the return to see what happens.

Might also be time to get the car jacked up and have a real close inspection of the lines, but I feel like I would have gotten some feedback while pumping 100psi through the line if it was kinked or crushed anywhere..

Are you only using the fpr guage or do you have another guage you can plumb in? I could lend you a guage set. Like if you plumbed it before the rail and pinch the hose after the guage you see if was a bad pump.

I wouldnt concern yourself with the vacuum portion on the reg.

I'm going up to Loo tomorrow and heading back home tomorrow as well, so I can grab and drop off the gauge set/anything else at Jeremy's.