I don't have any extra gauges that I can plumb in. I have a car until tomorrow night so I could drive out myself to borrow them.

But I'm not sure how a bad pump could cause this issue.. the gauge certainly seems to be working. Even if the pump was all over the place, the regulator should be able to hold reasonably constant fuel pressure. The fact that it can't suggest to me that the problem has to be at or after it...

Edit: When I searched around about this, I saw many people mentioning that they had to drill out a portion of the fuel return on the 2g sending unit when they went to a Walbro 255 with rewire. The fact that this setup ran fine for 2 years leaned me away from it; the fact that the return going into the tank seemed unrestricted pushed it right out of my mind. But I'm wondering if there's dirt or something in there plugging things up.

I'll probably pull my sending unit out for inspection after trying a few other tests..

Well a weak pump will run poorly untill you adjust the pressure to get it up to stock. but when the pump gets a surge of energy then it will raise the pressure higher then whatvyou set it to.

If the pump is running at half effieciancy and the regulator is set to create 45psi...then when it gets a sudden surge. It will spike the fuel pressure.

But the pressure doesn't spike from 43.5psi. It NEVER gets down to 43.5psi once the engine starts running. It fluctuates between like 48-55..

Jeremy I am with you on this one, I say after the regulator, seeing as you have now rules out the regulatore.
I would do what Jay initially suggested and hook up a return line into a bucket and then run some fuel into there and see what the pressure is like, that way you know for sure it's after the regulator.

So not much progress yesterday. I needed tools and some more fuel line and everybody was closed for the holiday... so I just cleaned the frack out of my garage, bathing in fumes

What I did manage to find out though: With the fuel system hooked up and the car off, the fuel pressure jumps about 10-12 psi when the pump turns on. It holds constant pressure with the pump running, then drops the 10-12 psi when the pump shuts off and holds again at the lower pressure.

Then, if I pull the return line off where it attaches to the sending unit and run a line out to a bucket, with the car off, and run the pump, it only jumps 3-4psi when the pump turns on. This suggests to me that there is some sort of restriction inside the return portion of the sending unit.

For tonight (time permitting):

-Try to get the sending unit out (I hear this is easier said than done... and the 14mm tube nut at the bottom of that rubber feed line from the sender was rounded by the previous owner)
-Disconnect the return line at the FPR and run a line from there to a bucket and see how fuel pressure behaves

Removing the sender is very easy. It's cracking those nuts that's a PITA. Vise grips are your best friend

Get a move on things! You're falling behind

Yeah, no sh!t. Unfortunately, moving into a new house, finishing up research while starting full time work, and having to juggle a half dozen family obligations in the past few weeks has really taxed my free time. Especially since I have to rely on Guelph Transit to get me around.

If I had a car, I would have had the time to fix the car. Catch 22 is a much funnier book than reality

I feel your pain, House projects taxed all my 'DSM' time

Didn't make it to the garage until about 9 (I had soccer after work). Ran the fuel pump with a line off the regulator straight into a bucket, and it acted the same as when the return was hooked up but not attached to the sending unit. So I'm quite confident that my return line is fine.

Pulled the sending unit out. Got the feed line apart at the sending unit (a day soaking in mouse milk and it was cake), and actually managed to get it off without ripping the rubber section. Since I really see no easy way of putting that piece back on, and I've already got everything apart anyway, I'm thinking of having the sending unit welded for -AN lines.

Took a look at that plastic piece where the fuel drains back in, and WOW is it small. Gave it a shot of air, and a little black something-or-other came out (I proceeded to burn it while cackling maniacally over the pitifully small flame). Again, since I'm already in there, I think I'm going to drill that little return hole out a bit.

Hopefully that was the issue. I won't have it ready for welding tomorrow, and my Thursday night is full, so it may not be reassembled until Friday...

I've tried searching a bit on this subject, to no avail:

Is there an easy way to get the white plug out on a 2g sending unit? It looks like the metal is crimped on the sides to hold the plug in, but I don't like bending things out of shape if I don't have to.

Nevermind, got 'er out..

like this?

Try building a DSM from the ground up with the car 2.5 hours from home. Quit yer belly aching

I don't envy your situation either, but I do love your work.

Progress!

Got the fuel system back together last night with the new feed and return line. As soon as I tested the pump, it was obvious that the return had lost a significant amount of restriction.

Fired her up, she ran SIGNIFICANTLY better, with the fuel pressure acting absolutely as it should. It sounds like the engine is quite a bit out of time though, and it had trouble running below 1500 or above 5000 RPM.

I'm trying to figure out exactly how to do my base timing. Apparently the '95s DID have a plug that you could ground to put the ECU into base timing mode, but I'm not sure if that works with the AEM EMS. From what I gather so far, I need to figure out what my base timing is set to in my tune, and then match the actual base timing to it. I may have to do the "set-timing-while-cranking" method, and just hope my starter keeps running like a champ.

Hell, it managed to survive me trying to start a seized motor with it..

Good stuff!! What are you using for air measurement?

There might be an option in AEM to set your base timing, I think I would look for that first before trying to ground stuff.

Lets see some picture of the fuel sending unit!

GM IAT and AEM MAP sensor for SD (as far as I know), and yes I'll be digging through the AEM stuff tonight and poking around on their forums.

I'll see if I can get a pic of the sending unit.

Oh ok, when my car had a leaky 3' maf it was having the same symptoms.

I'm thinking the timing being out has something to do with it.

If not, I'm guessing the problem will be easier to find once the timing is right

Okay, so the problems persist. The fuel pressure is acting perfectly normal after the new lines, but the engine still seems like it's getting way too much fuel. It takes a ton of cranking to get it running, and once it's running the AFRs stay pegged on rich, it stalls if you try to idle, and it can't get past about 4500 RPM before it starts misfiring and popping away...

I'm going to try and get a log of it while it's running, and I'm awaiting approval to begin using the AEM forums. I really feel like it's not going to be a tuning thing though; it ran fine on the same tune before the rebuild. I'm sure it will need some tweaking but it should be close enough for the car to run.

Not even sure where to go from here. Maybe pull the injectors and test them... I'm really starting to get frustrated though.

I'm sure you have but did you do a BLT?

There could be an issue with the tune now that youve fixed the fuel issues, after an engine rebuild there will be a difference in compression and vacuum due to the new parts, your old tune was smoothed out to another engine basicly (as far as the ecu thinks)

My tune was perfect for my engine before it went in for a rebuild but the ecu was tuned around cracked valves and a blown HG, when I finally get the engine back it would be in my best interest to go over the tune from the start and make adjustments to dial it in for the new conditions.

Yeah, BLT was fine. I know the tune will need to be changed for the new engine, but the old engine held compression fine, had the same compression ratio, same cams, same valves. It should need smoothing out, but I can't see it needing to be redone from scratch..but we'll see what the logs say when I get a chance.

How does AEM adjust fuel? Is it like Link? By that I mean you set your base Global and deadtime then tweek from there. I remember mentioned the front wiring just laying there, Is your WB installed in the front O2 or downstream? Is there a NB sim in AEM?

I know that AEM read WB natively, huge plus I think.
Did you change injectors, I am sure AEM would be total dead time and not just the stock plus what ever you enter.

Found this, does it look like this:

I don't think there's a need for NB sim as there's no stock ECU to keep happy. As Bryan said, AEM reads the WB natively. I'm not sure exactly how fuel is managed (haven't gotten that far yet..), but there are big charts like what Bryan linked where you can adjust the numbers (and when you put in a bigger number, it puts in more fuel).

I've made adjustments to the fuel map before but all I did was click on the boxes in the chart and fiddle with the numbers a bit..

Edit: To answer your question Bryan, it looks similar to that. That's AEMTuner, I'm on AEMPro (I think the Version2 guys use AEMTuner).

Oh right AEM is a stand alone... I have seen alot those (in the honda world) that over the winter didnt keep settings. I have even seen them lose everything if you turn off the key, but that of been incorrect wiring.

Probably AEM forums are your best advise or join the sheep and buy link... (still don't know how to put in emoticons)

The thought crossed my mind too. I reflashed the ECU last Tuesday, and again yesterday before firing it up.

I want to get on the AEM forums but you have to wait for approval, so I'm guessing that won't be until tomorrow. I may try to make a new base map just to see if I can get it running better; if I can, then I know it's in the tune.

when writing a post at the bottom of the screen it will have a button that says 'switch to full screen reply' click that and at the top left of your new window it will have a smiley face button...click it and chose what emoticon you wish to use.

I always thought emoticons were for teenage girls.

...wait I don't get it. This sentence is completely free of grammatical or spelling errors.

Who's on Jay's account?

Hahaha!.. ''

I am actually killing myself right now

All in good fun Jay

I think while I wait on approval for the AEM forums I'm going to go back to basics. Check spark, check injectors for leaks/spray pattern...

Make sure the coolant temp sensor is plugged in

If you need Injector testers. I can lend you one.

What does the tester do/how does it work?

It test resitance and flow in conjuction with a fuel pressure gauge to check for leakage and flow balance.

So, I went about checking the basics tonight. I got the plugs out and laid them across the valve cover with wires attached, pulled the CAS and put my key in. Gave her a spin, and watched the pairs of spark plugs fire away, happy as can be. Gave her a couple more spins, and noticed something. The second and third plug were firing as the CAS was passing by the position that you set it to when installing it for #1 TDC.

So.....


......out of curiosity...


..can these cars run if the plug wires are on opposite coils? That is, cylinders 1 and 4 are firing when 2 and 3 should be, and vice versa?

It was too late for me to be able to switch them back and fire it up to try.

CLICK ME!

I set mine up according to how you're supposed to if you have a 6bolt in a 2g using the 1g coil pack and igniter. But with AEM you can set it up either way, and I'm too AEMtarded to know how to check.


P.S. Dick

Hey that was cool