Hey guys, so here's the situation I'm in. I bought an 89 IROC-Z about 2 months ago that had its 305 TBI swapped for a '91 350 TPI setup (including an ECM swap, and painless wiring harness swap). The guy who did the swap never got it running. The fuel injectors would not pulsate, but he said when you sprayed some starting fluid into the throttle body it would pop a couple times. Initially I thought it was just an easy fix that would require a VATS bypass (stupid me) so the car is also hooked up with a mostly stock MEMCAL programmed by Scott Hansen (who has been very helpful to work with) including a VATS delete, and speed limiter delete, maybe a couple other things.

What I found was a complete wiring mess that I've slowly been trying to sort through but most of my attention has really been focused on getting her running.

In the last week and a half or so my Dad and I went through and reset the distributor and checked plugs and wires (the prior owner actually had the 6 and 8 wires switched). We went to start it and all it would do was crank, so we checked for spark and we were definitely getting it. So we went ahead and sprayed starting fluid in and it actually ran (which was so nice to hear) until the fluid burnt off. But it was still clear that there was a fuel issue.

The next night we didn't have all that much time to work on it. We made sure the pump was priming and checked if we were getting fuel at the rail and we were. So after that we put in the hold down for the distributor, and I decided before we went in for the night I had to hear it run again. So this time, instead of using the starting fluid, which my Dad and Grandpa kept telling me could damage the engine, I threw some gas in a spray bottle. The first couple times it would just start and run until the gas burned off but the third time, it wouldn't die and it kept going for about 20 minutes before I shut it off.

So that's great and everything, but problem is it won't do anything more than idle. There's also basically no throttle response. When you open up the throttle, you can hear the engine kind of race up but it just sounds like its getting starved and you will also get an occasional pop or backfire. We tried to do some timing while it was running, but while my Dad was running the gun he kept saying that something wasn't happening that needed to be because the timing wouldn't adjust (I found out later that night that you have to bypass the EST for timing).

So do you guys have any ideas on what could be going on? My Dad and I were thinking it might have something to do with the TPS but I really don't know.

Hopefully you guys can think of something.

 

Anybody?

 

The 91 is a MAP(speed density) car. The symptoms you describe, including the fuel related hard start sound alot like a MAP issue. You need to be sure that the MAP is connected directly to manifold vacuum with nothing else tee'd into the line. Verify fuel pressure with the engine running. Pressure should increase from 35-40psi to 45-50psi as you rev the engine. One would think that the swap included a high pressure PFI fuel pump, but don't assume, verify. The TPS is not a likely cause of your symptoms. Now that you've had the engine running, check codes to see if the ECM has detected a problem.

 

Don't assume that the other guy replaced the FP with a high pressure one. If he messed up so bad on the wiring, who know what else he did wrong. Good luck!

 

I do know that it's a high pressure fuel pump, and I'll have to look into the MAP. Now that you recommend I check codes, that brings up another issue. From what I can tell, my ALDL connector is not working. When I jump the two terminals nothing happens, and there's no check engine light. Could this be anything other than the ALDL not being wired to the ECM?

 

That or the CEL light is either disconnected or the bulb is out. Does it light up when you turn the key on?

 

Yes it does

 

Have you checked the map yet?

 

I checked the MAP and from what I can tell it is the only thing hooked up to the manifold vaccuum.

 

It sounds like the ALDL may not be connected properly to the ECM. The only thing I can suggest is dig in to the wiring and see where the wiring is cut or disconnected. Personally, I can't see the reason for using a painless harness on a swap like this since the cars(donor and recipient) are essentially identical and the ECM harness from the 91 would plug right into the 89 with some repinning of connectors. The issue with painless is that they are anything but painless and give you just cut wire ends to deal with. It's likely that the installer hooked up what he thought he needed to get the engine running and left the rest hanging.

As a professional, I would probably tend to run away from a mess like this, unless the owner was ready to pay for alot of time rewiring and correcting the ECM harness. Otherwise, you need to purchase the factory service manual Electrical Supplement for the 91 (or somehow access factory level diagrams) and use it as a guide for properly connecting all of the ECM wiring. Otherwise, it's hard if not impossible to even guess what the installer may have done.

One possible option to the factory book is All Data which features scans of the factory diagrams. All Data is available online at most public libraries and you can just print out the diagrams.

 

 

Yeah, I'm not at all impressed with this Painless setup. Come to find out, the regular Painless replacement harnesses are about 2 feet shorter than a stock harness (they said something about it being better to mount the ecm in the engine bay). In order to get a regular length harness, you have to order the Painless Extra long harness.

On top of all of that, the prior owner actually told me he didn't know what he was doing with electrical (IT SHOWS!!!!) and that he was basically taking instruction over the phone from Painless. And you're right, there's loose ends all over the place. I've inherited one hell of a mess.

 

The ECM in the engine bay?! That goes against everything I learned at GM. The later sealed case ECMs and PCMs are a different story but these early, non sealed ECMs will drop dead quick in the presence of moisture. I don't know what planet the Painless engineers live on but here on earth, moisture is often an issue. Even on my Beasty, that never sees rain, I wash and wax the engine bay as often as I wash and wax the car. Definitely do not mount your 91 ECM in the engine bay.

I'm sorry for your troubles, but with work and care you can fix it. Just take your time and make the repairs the right way. For wiring repairs, solder and heat shrink are best. Not quite as good but acceptable are heat shrink butt connectors.

 

Hey guys, since I got home from school for the summer I have been slowly working and trying to figure out what the problem is with my car. I still have a feeling that my injectors still aren't pulsating. I went through and ohmed the injectors, and were all good (between 13.9 and 14.0 ohms). Nonetheless, the car will not start without starting fluid, and most of the time will only run until the starting fuel goes off.

My most recent step was to look more into the fuel delivery system. So I pulled the feed line right before the engine, and when the pump is primed, fuel does come out and when the engine is cranking, gas still comes out. So next I looked into the fuel pressure regulator a little bit and tried to make sure it had a good vacuum connection. Unfortunately, the vacuum line situation in this car is about as much of a mess as the wiring is. But after making a seemingly better vacuum connection, there was no improvement.

So next, I bout a fuel pressure gauge, and hooked it up to the schrader valve on the fuel rail. Although I wasn't expecting a great number, the 0 psi I read came as quite a surprise. So, there is so little fuel actually in the rail that it isn't even registering on the gauge.

I'm not really sure what to do next and am running out of ideas. I was thinking I should pull the plenum next and try to get the vacuum situation a little more straightened out. You guys have any ideas/suggestions/recommendations/clues/theories as to what could be going on or what I need to do? I know I read somewhere that a bad ignition control module will lead to the injectors not firing, but if I had a bad module, I don't think I'd be getting spark either which I definitely am. I don't know guys, I'm more frustrated now than ever.

 

Any ideas guys? I'm damn near out of them

 

Alright sooo today's my birthday...so all you guys with far more knowledge in this stuff should help me out as a present haha. Just kidding, but really if you have any inkling of what's going on I would really appreciate it.

 

I believe I'd start w the 0 fuel pressure problem. If you dnt have any fuel pressure the injectors won't spray even if they are pulsating.

 

Agreed. Any idea that would be? The fuel pump is damn near brand new and is a sufficient model for the 350 TPI. I've heard that fuel filters can be troublesome, any simple way to check them?

 

Is the regulator in good shape? I dnt know a simple way to check the pump other than the shrader valve. Fuel filters are cheap and easy to change, may be worth a shot.

 

You first need to make sure your fuel pump is getting power. You should have a fuel pump relay that is controlled by the ecm and possibly an oil pressure switch. You can jump the relay to make the pump run, just be sure to jumper the signal to the pump and not the signal from the ecm that turns the relay on. You definitely need to get fuel pressure in order for the motor to run. I wouldn't worry about your regulator until you get the motor running. Work on the fuel pressure first.

 

The fuel pump is definitely getting power...when I pull the fuel line before the rail and either prime the pump or crank the engine, I get fuel.

 

Correct me if I'm wrong here, but doesn't the regulator regulate the fuel pressure? If he's getting power to the pump and getting fuel if he disconnects the line then Why would he not need to check the regulator? If its bad inside it'll just circle fuel through the rails and right back to the tank and never pressureize the injectors.

 

So how do you check for a bad regulator?

 

Take it apart and inspect the diaphragm and spring.

 

Alright. You have to pull the plenum to gain access to the regulator, right? If that's the case while I have the plenum pulled I'll try to go through and sort out the vacuum situation while I'm at it.

 

Yes I believe you do have to take the plenum off. There's threads here w vacuum diagrams for every model.

 

Just pull the vac line off the regulator, if it has raw fuel in it its bad. No fuel, its good.

Check the fuel PSI
Set timing properly
OHM injs if they are stock.
The TBI harness can be adapted to a TPI so easy its not funny. People create such a mess when they do what the PO has done to this car..

The painless harness is easy to use if you have a streetrod.

 

You may be money and time ahead to just scrap the painless harness and find a factory TPI or TBI harness and start over.

 

The question is, how much fuel? Just because you get fuel doesn't necessarily mean you have good pressure or volume.

 

You are correct, but there is enough of a restriction in the return that the pump should make some pressure. Even if it is only 5 - 10 lbs. At least enough to show on the gauge, I would think.

 

Alright, I pulled the vacuum line and it didn't have any fuel in it. As I mentioned before, the gauge does not even read pressure at the rail, but I know there is at least some fuel getting through. We set the timing to top dead center as best as we could but couldn't time it with it running because we haven't been able to get it running long enough. The injectors have all been OHMed and read between 13.9 and 14.1 ohms. So what's your thoughts knowing that? Bad fuel filter? Maybe even a bad ECM?

 

To eliminate the regulator/pump being the problem, try to deadend the return line. The pump should then build pressure if it is running and you have no restrictions in the supply side (clogged fuel filter). I wouldn't run the pump too long with the return line deadended as it will stress the pump, but you should be able to see pressure on your gauge within a few seconds. The line can be accessed at the front of the manifold. Let us know what you find.

 

Alright. This seems very strange, with the return line plugged, there was still no change in pressure

 

Not so strange, you are back to square one. You say the vats has been deleted from the prom so that should not be a problem. You are not getting fuel to the motor for whatever reason. You need to do a step by step troubleshooting of the fuel system. First, make absolutely sure your filter is not plugged. From there, you need to determine if your fuel pump is running and if not, why? I mentioned in a previous post in this thread, that you can jumper power to the fuel pump to bypass the relay and power the pump directly. I think the fuel pump relay is on the fender well (in the painless harness, you will have to figure out where it is). Once you do, pull the relay and with an ohm meter, check across the pins to determine which pins are the coil and which are the contacts for the pump power (the coil pins will likely read somewhere around 15 to 25 ohms). Be careful and match the contact pins to determine which pins in the harness connector match. Place a jumper across these two pins in the harness to apply direct power to the pump. This should power the pump once you turn the key to "on". Check your pressure gauge to see if you are getting pressure at the rail now. If yes, start the car and see if it runs and can accelerate. If you still don't get pressure, you will have to go right to the harness connector at the top of the tank. Unplug the pump connector here and see if you have voltage across the pins with the key "on" (harness connector). If you determine the pump is running and you still have no pressure, could be the pump is cavitating in the tank. Check these things and let us know what you find. Good Luck!

 

Something else to check.
If some one has changed the fuel pump b4 and put rubber hose in place of the pulsator it could be bad and just blowing fuel right back into the tank.

 

Big Al, I'll look into that stuff as soon as possible, thanks.

In regards to the pulsator, from my research I thought that the pulsator was essentially there too reduce fuel pump noise and could be replaced with high pressure rubber hose, is this correct? If not I will definitely have to look into this as I know there is a lot of high pressure SAE hose in my fuel line.

 

The pulsator is a dampener for the psi pulsing the pump does. It can be replaced with hose.
In the tank you have to use submersible hose or it will fail, even if you use EFI high PSI rubber.
http://www.napabeltshose.com/fuel-de...bmersible-hose

 

Ok, so basically if my pulsator was replaced and was replaced with regular fuel line, there very well could be a hole that has been developed and only a small portion of the fuel being pumped would actually be making it up the fuel line.

Another question, would it really make sense for a fuel filter to fail or be clogged so much that it would prevent almost any fuel from reaching the rail?

 

Yes and yes it can happen.

 

This is only my opinion but, considering the newness of the parts involved, I wouldn't think the line would have a hole in it. You said the previous owner just put this system together and couldn't get it to run, right? This is not to say the po did everything right, it's possible he/she didn't connect the pump lines up correctly or at all. The point is, you will really have to dig into the fuel system as a whole and correct any problems you find. If you want a good reliable car, it sounds like you're going to have to go over everything the po did. As for the fuel filter, yes they can get clogged that bad. Possible that when the po put the new pump/pickup in the tank, sediment in the tank could have gotten stirred up and transfered to the filter where it just packed in there tight causing a clog. Do a systematic check of the complete fuel delivery system, starting at the tank and go forward until you are sure you have corrected the problem. You say your lines have a lot of high pressure rubber hose. This should make the process a little easier. GL and let us know what you find.

 

Well I got around to checking the fuel filter today, and it was fine. So unfortunately it looks like I'll be dropping the tank next

 

Any progress? Let us know what you find.

 

Hey guys, sorry it took so long to get back, life kinda got in the way for a couple of weeks. Today I finally got around to dropping the rear end and pulling the tank, but didn't have time to open the tank. Hopefully I'll have some time to do that tomorrow.

Here's my game plan on what to look for:
Clogged strainer
Rusted out tank
Holes in pulsator
Bad pump (how exactly I'm going to check this I am not yet sure of).

Anything else you guys can think of to look for in there?

 

Well did you disconnect fuel line near motor and check if gas is flowing good? IF it is, then i will suggest you go buy a electrical tester or what ever the little screwdriver things with lights that test for current are called, then go test all the wires that go into ecm and are supposed to have power to them when key is on, check injectors for actuall power first as this was my issue once. Also check injectors directly at their harness for power whith key on and cranking it.

 

By the way the tool is less then $8 so go buy it and it will clear up quite a few issues if your injectors are getting a actuall 12volts to them.

 

Looks like you guys were definitely right, looks like the PO definitely replaced the pulsator with regular fuel line and its real beat up and theres a split running almost the whole length of it.

 

Replaced the pulsator with the submersible hose from NAPA that (if I remember correctly) TTOP350 recommended, and hopefully tomorrow I'll have the tank back in and ready to go. And P.S. (as I'm sure all of you guys know) it was a BITCH to get the tank out, so I'm sure it's going to be a bitch to get it back in as well.

On a side note, before the car can really get off the ground and running I'm also gonna need a panhard rod. The thing was warped to **** and almost actually cut all the way around towards one end. I might even need to replace the brace. O well, another thing to throw on the list.

 

IT'S ALIVEEEEEE!!!!!!!!! Of course I found a massive fuel leak after it started running, but ALIVE nonetheless.

 

Now we just seem to be having some timing issues. We timed to 6 degrees as Scott Hansen instructed and it still idles pretty rough and backfires under throttle. We will be resetting the distributor but I don't think that's the problem. And we timed it with the ESC unplugged.

 

Great! Really glad you got it going. Check your injectors to be sure they are all firing. If
you don't think it's a timing issue, check to be sure you have no vacuum leaks. Hows the fuel pressure now? Plugs and wires all good? Check all the basics. Good Luck and keep us
up on the progress.