All,

I have a 1990 IROC Z, with a 305 and TPI. I do not drive it everyday....so it does sit (covered) in my driveway quite a bit. The current problem du jour is that the car will start and run for a period of time....maybe a half hour, maybe longer. Then, it will die for no apparent reason. When I try to restart, problems ensue, and it ultimately takes spraying carb cleaner into the throttle body to aid in the starting. Spark Plugs are fairly new, as are plug cables. I have replaced the fuel filter. I think it may be an intermittent fuel pump.....but wanted to ask for advice before I attempt a fuel pump replacement....which looks like a chore.

Any sage advice on this?

Thanks
Jim

 

sounds like a pump

 

I would ohm your injectors too.

 

Eliminate any other fueling related issues and then attempt to do the fuel pump. Doing a pump in these cars sucks and I would hate to go through that trouble to find out that wasn't the cause of the problem.

 

I agree with Ryan.

 

fuel pressure test when its acting up would tell you

 

Thanks for the advice. But, outside of replacing the fuel filter, not sure what else I can monitor to make sure Fuel pump is the problem. Outside of draining the gas tank and seeing if it is just the gas that is the issue. I did put in a gas additive to try and make sure gas was not the issue.

What should the resistance of the injectors be?

 

What do I need to perform this test? And where do I look? I am not a novice mechanic, but not a pro either.....

 

You should check your fuel pressure (rent a kit at autozone or any other parts store), but you should be able to hear the fuel pump priming when you attempt to restart the car after it shuts off. When it dies, turn the ignition off for at least 10 seconds, then turn the key to the "on" position and you should hear your pump run for ~2 seconds. If that's not happening, chances are it's failing when it gets hot. You can also buy an injector test light, which plugs into the injector and the harness in series and blinks with a properly operating injector. Checking the resistance (or impedance specifically), can also be done. From what I've read, anything below 12 ohm's should be replaced. You'll need an ohmmeter or a digital multimeter for that. Another thing that could be the culprit is the ICM, or possibly the pickup coil inside the distributor.

 

Thanks for the specific advice Ransford2987. I will visit Advance today and see about that fuel pressure kit, and the injector test light. I am a electronics tech, so have a fluke and know how to use that piece of test equipment. I read in Haynes manual about replacing the fuel pump, and it does not sound easy.

Hopefully, can get this problem figured out, then get a piece for my convertible top so I can have that replaced....and my car will be back to running reliably, and looking good as well.

 

should not be less than 12ohms. If you do decide to check them, be sure to check them when they are hot,,, bad coils tend to fail when the injectors are hot

 

Been miserable weather here....my camaro sits in my driveway under a cover....so have not been able to do much.

I purchased a fuel pressure gage, and see where the schrader valve is.....my question is what should I see there? When is there supposed to be pressure, and what is the magic number?

 

If your car has been sitting for a while, you'll need to prime the system. Hook up the gauge to the schrader valve and make sure you have a rag or something around it to collect the fuel that sprays from the valve. Continually turn your key on and off, waiting a few seconds in between until the pump runs for its two second interval and then shut off. Or you could just start it up with your fpr disconnected and let it run for a bit until pressure is normal, ~ 42-47psi is the spec IIRC. You'll also want to check that pressure does not drop once the car is off, so shut it off after you verify running pressure and see how much it drops over the course of a few minutes. You shouldn't have very much of a drop; from what I've read not more than 1-2 psi for 5 minutes or so. I think that might be "acceptable" not necessarily good. There should be some more in depth threads on here about checking fuel pressure, so give it a search.

 

Ok....finally a nice day here and I hooked up the fuel gage to the schrader valve. I saw 42psi on startup, then the car would idle around 36 - 38 psi. The car started up normally, and ran for approx 7 minutes, then died. Fuel pressure remained at 36-38. I tried to restart the car, but it would not start....like either fuel or spark was missing as engin would turn over, but not start. I sprayed carb cleaner into the throttle body, and car would catch/start for a minute, but quickly die off.

As I had a pressure reading, and it remained same when car died, does that mean fuel pump is working normally? It is a little low from what was recommended....but still not 0.

Would bad gas/water in gas line cause something like this? Or is it more likely some type of spark/plug issue?

I have not checked injectors yet as I forgot to bring home my multimeter from work, so that will have to wait until tomorrow.

 

You can start with checking the injectors, and you need to check them when hot. From there, if none are the issue, I would check your ICM or your pick-up coil inside the distributor. The pickup coil generates a signal to the ECM used for telling it the engine is running and to begin injector firing. When mine went bad, it completely failed at power and I couldn't restart it; but I've read stories of people with bad pick-up coils that faulted with heat. A faulty ICM could be losing spark when it gets hot.

Did you check your fuel pressure without the fpr connected to vacuum? If pressure held relatively steady after shutdown, then I would rule out your fuel system, other than possibly injectors, being the problem.

 

ICM = Ignition Control or Coil Module? I will check injectors tomorrow......but interesting you should mention items around distributor as this is what someone who happened to be at Advance Auto when I was there buying the fuel psi meter told me.

FPR ? I did not disconnect anything, just attached the meter to the schrader valve.

 

ICM = Ignition Control Module. It's buried in your distributor. You can test it with that DMM you plan on bringing home, but it takes a little bit of work to gain access to it. FPR is Fuel Pressure Regulator. It's on the back of the fuel rail. It affected that 38 psi or so reading you were getting. You probably would have been where you needed to be, so I wouldn't worry anymore about pressure. If you decide to check the ICM, take a look at the pickup coil inside the distributor while you're at it. If it's excessively rusty, I would just replace the Dist, as reman ones come with an ICM, which is a $50 part anyway, and the whole Dist is around $100. It's worth replacing the ICM and Dist together, as you have to use some heat resistant dielectric grease on the bottom of the ICM anyway. But, that's if you check your injectors and all is well with those. You can also check your ignition coil with that DMM. Access to that is easier, as the connectors are right on top and it sits on the passenger side, rear of the engine. I'll add some pics of the pickup coil for your viewing pleasure, so you know what I'm talking about. The coil is the rusty thing in the middle, and the ICM goes on the bottom. You should see some grey grease, and a bolt hole on the bottom left.

 

Ok....checked the injectors today. Car acted a little different, had been sitting for a day, and it started but ran real rough....could press the gas pedal to the floor and engine would just not rev up beyond stuttering. When I sprayed carb cleaner down intake, it would rev up and sound normal.

I let it idle very rough for a few minutes then cut off car and measured injector resistance with a Fluke 177 DVM. Found that 4 injectors were at 9 ohms or less...a couple were at 4 ohms.

So looks like first issue is to replace some injectors. How often do these need to be changed? Would it be better to replace all at once? Others were at 12 ohms - 15 ohms. Car has 130k original miles, no rebuild of engine or anything that I am aware of. I am 3rd owner.

Thanks for all the help thusfar....

 

http://m.southbayfuelinjectors.com/p...7&product=1500
Replace them all

 

The injectors need to be changed. Yes they all should be replaced. The stock injectors are junk. Newer style injectors will / should last for years.
Get yourself a set of Bosch lll's


Sorry, looks like you beat me to it!

www.southbayfuelinjectors.com
516-442-4707

 

Thanks for the link.....am going to call South Bay tomorrow just to make sure I get all that I need for this project.

If I am reading the ad correctly, it is $155 for a set of 8? That is pretty good considering Advance Auto wants anywhere from $50 - $90 apiece.

I have a Haynes manual, and also found an article on this site about replacing the injectors....looks like an all day sucker there.

Anyhow, is this the most likely cause of my issue, or merely a problem but I may have something else going on?

 

I wouldn't say its a all day job, gasket and part cleanup take the most time. it doesn't take more than a hour to swap out the injectors and clean off stuck gasket material. the Multecs have gone to the grave and have been shorting out shutting down the injector driver. replace your fuel filter, injector crossover tube o-rings, injectors and would be a wise idea to get a new for diaphragm while your at it.
https://www.thirdgen.org/forums/tpi/...uel-lines.html

 

Tuned performance,

Thanks for the link, but to get to the injectors one has to disassemble everything on top of them, correct (per Haynes manual and the instructions posted elsewhere on this site)?

What is the diaphragm you are referring to? I had already replaced the fuel filter as part of troubleshooting this issue. And am looking at the O ring kits as well...as sure I will need to replace those.

Thanks!

 

If the coolant hose is still ran through the throttlebody iac plate just remove the 4 10 mm bolts holding on the tb and let it dangle. Removing the serpentine belt to gain better access to the fuel fail lines and the 9/16 head fuel rail line retaining bolt. You don't have to pull more remove the runners but if you decide to take off the valve covers to make it easier to get to the lower hidden and lower runner t45 bolts.
the fuel pressure regulator is on the back of the fuel rail, you will need a anti tamper torx.
http://m.southbayfuelinjectors.com/p...7&product=3054








Pictured above is the typical set up for a 1986-89 MAF based system. Speed density is similar. (A) Intake manifold. (B) EGR valve (C) EGR temp switch (maf only) (D) PCV fitting, to the left is orifice for cold start injector (maf only) (E) Thermostat housing neck and bolts (F) Bolts needed for top plenum and runners- 13- M8x1.25x30mm, 2- M8x1.25x40mm, 4- M8x1.25x50mm, 1- M8x1.25x30mm throttle bracket stud, 20 total, these use a T40 Torx head bit, NOTE these are metric. (G) Fuel rail typical for a "F" body, maf system, fuel lines for Corvette is on opposite side. Look at picture, as this is a complete system (H) cold start injector and fuel tube (maf only) (J) Fuel injectors-8 total (K) Intake runners, speed density will not have the cold start opening (L). (M) Intake air sensor (P) Intake plenum, with throttle body, be sure to get complete throttle body with no missing upper and lower cover plates, bottom plate has provisions for IAC and coolant tubes. (Q) Throttle bracket and bolts (R) Vacuum fittings for fuel regulator, heater control and brake booster, speed density will have a fitting for MAP sensor and mounting boss.

 

TP, thanks for taking time to post that. MY engine does not look immaculate like the one in your pics!!!

I ordered the injectors today from South Bay....spoke with the rep there...can't beat that deal. Will be a couple of weeks before I get back to this due to my work.....but will post results and/or additional questions...

 

Ok, finally got to replacing the injectors on my car today. Am in the disassembly stage right now to get to the injectors/fuel rail....using the guidance in both the Haynes manual, and the TPI injector swap by jasonlitka on this site. Couple of questions:

1. The procedure mentions removing each of the runners from the manifold. Why do I need to remove the runners? Also, it mentions 6 bolts per side, I can only see 4 per side.

2. I noticed that the top 2 air holes on the runner (ones closest to the driver) were "dirty".....whereas the other 6 were pretty pristine. What could have caused those rear two to be dirty like that?

3. What else should I replace now that I am into this area of the engine? I did NOT notice any oil leakage/spillage.

4. What is best cleaner to use to clean up engine, and is there a spray paint or something that I can use to make my parts look like the ones pictured above?

Got dark prior to removal of the fuel rail, and I wanted to know if I really needed to remove the runners as a couple of those T40 bolts are in areas that will make them a pain to remove.

Thanks

 

Speaking from experience (I just did the same thing about a month ago):
1. You have to remove the runners to get the fuel rail out. If you look at the photo above you can see all six holes for the bolts. The front bolts, if I remember correctly, have to be accessed from the intake manifold side (and I think its more like 8 per side).

2. That's the runners closest to the EGR inlet on the plenum. I wouldn't be to worried about it, however, I did go through and clean my intake up quite a bit (EGR passage was actually clogged).

3. While I had the car down that far, I did the thermostat (I'm pretty sure mine was sticking). How much you want to do will depend on you. There are several vacuum lines that I would replace if the look like they might need it.

4. I used carb and throttle body cleaner on my intake. However, my egr passage was so clogged, I ended up using a pick to break it free. As for just cleaning the rest of it, I'd start with some simple green, after blowing it out with carb/TB cleaner. Paint is entirely up to you, but make sure its high temp.

 

Nomind,

Thanks for the advice and suggestions. May replace the EGR just for General purposes....and I read on another thread to replace Intake Air Temp as well as look at vacuum tubes and hoses and associated gaskets.

Hopefully I can get out of work early today and continue my repair work....

 

Been traveling with work so working on this in my spare time. I have everything apart, and am in process of cleaning, repainting the air tubes....and figuring out what else I want to replace now that I am down this deep into the engine.

Friggin star bolts were a pain in the rear to get off.....there were a couple that were especially painful.

Have the replacement injectors mounted on the rail.....hope to get everything back together this week.

Also does not help that this is probably the coldest weather that we have had in recorded time here in Va. Bch......

 

I looked at the distributor today, and indeed it looks like the picture that you provided. So I assume that it will need to be replaced as well. How do you replace the distributor assembly? Did a search on distributor, but did not come up with anything......maybe I searched incorrectly. Am going to parts store now....yet again.

 

Ok...I purchased a replacement EGR (just because it is probably at least 13 years old, and easy to replace now), and replacement Distributor.

Reading the Haynes manual, looks like only one clamp bolt holding distributor in. Guess my question is where is best place to mark distributor before I remove the old one? Right now, looks like rotor is pointing toward drivers side of engine. Haynes manual mentions something about 2 marks....but seems like I just need to pay attention to the placement of the rotor. The ICM is toward rear of engine.

What else do I need to pay attention to when replacing the Distributor?

 

Ok....I marked the position of the rotor, and removed the retainer bolt. However, the distributor does not seem to want to just lift out of the engine block. Are there any other bolts that I am missing? I thought there was only the retainer and the 2 electrical connections for the ICM that needed to be taken care of.

 

There shouldn't be anything else, just wiggle it a bit to get it loose from the cam or the oil pump, whatever it's getting caught up on.

 

OK...I got the distributor off. Unfortunately the new/replacement one does not want to align with my marks....and neither does the old one when I try to reinstall. Looking at a youtube vid on distributor replacement by MSD folks...they tell me that for an engine that was already running, and replacing the distributor, look at where on the distributor cap the rotor is pointing, and align same for new distributor.

It looked like the old setup had the rotor aiming at the #1 cylinder. That is how I have the new setup installed. Is this accurate?

 

The rotor will face where ever you marked. but not to say you won't need to turn the oil pump shaft with a long screw driver. or drop the distributor body up and down while the rotor is about a tooth or half a tooth off. When the distributor seats the cam gear will rotate the distributor gear slightly.

 

Like what tuned said, just make sure it's close to where it was, assuming you're putting the spark plug wires back on in the same order. If everything else is the same, there will be a slight difference in the rotor position which you'll have to set once you get it running. You have to get it close so it starts correctly and you can set the base timing.

 

In addition to the advice here, and in my Haynes manual, I found this video on distributor replacement:


I think I am ok based on this video, but I am going to play around more with the seating of the distributor.....see if I can get it to my marks. It just seems to go in easily, and fully seat, in the position I currently have it....which is a little off the original marks I have. When I try other positions, it does not seem to fully seat.

I have the #1 plug cable/position on the distributor cap over the rotor now....just like it was for the original setup.

I just want to make sure I do not damage the engine when I finally start it up.....

 

That's what tuned was talking about with putting the screwdriver into the dist hole to move the oil pump rotor slightly. The bottom of the dist can only fit onto the oil pump 2 ways, 180* apart. That's why the bottom of the dist almost looks like a flat head screwdriver. If it's close, your timing will be close enough to start, it will, albeit rough.

 

Rg what you say...makes sense concerning the oil pump rotor and alignment. I just do not know why it seems to be aligned differently now. Maybe new distributor gear and bottom of dist are not quite aligned same on new distro as they were on original one.

Thanks for info...will be little while getting back to this as I have to go to Pearl Harbor for a job....hopefully Xmas here will be mild as that is when I will continue this project.

 

The oil pump can be moved freely, so any "wiggling" you do can slightly move it. And, as you may know, even the slightest movement is going to be a certain number of degrees off from where it was; this of course translates into a movement +/- your previous timing BTDC. But that's why it's different, and why tuned said you may have to turn the oil pump shaft slightly to get it back to where it was. It's definitely a tight fit, though, and may take some additional "wiggling" to get it installed again.

 

All,

I appreciate all the sage advice concerning my problem. I finally completed the project today.....replacement of the injectors and the distributor. Ended up taking the runners off a couple of times....initially had them on the wrong side.....couple of other minor mistakes in reassembly....but overall it went smoothly.

The moment of truth happened when I tried to start the car. After a couple of times where the engine turned over but did not start.....it finally started and seems to run fine....not really missing or anything. It actually sounds better, and seems to be smoother when I apply gas to the engine and rev it up. I took it out for a quick ride...not too long as the state inspection has expired.....and then let it sit in the driveway idling. It was on for around 40 minutes with no issue. I stopped and started the engine several times and each time it worked with no issue.

Time will tell, but I think that the issue has been resolved between the injector and distributor replacement. The car remained on for longer today than it did previously and at no time seemed ready to stall.

Again, thanks to all who made suggestions...and just the articles and threads in general as I perused many of them.