1988 Tuned Port Injection Problem
 

I recently bought a 1988 Corvette from a friend. It has been sitting for 3 years. It ran very rough. After new plugs the car ran very good. Then it sat for about 3 hours and when I started it, it ran rough again. It was flooded and ran very rich. I pulled the fuel pump fuse, started again and it ran smooth as it used up the residual fuel in the system. Then I put the F.P. fuse back in and re-started. It ran good again. Idled smooth and revved well throughout the range. Seems when the car is off fuel leaks through some injectors and floods the cylinders. Any thoughts??? I guess you can tell I have no experience with fuel injection. When I jump A & B on Diagnostics plug it shows no stored codes.

Sounds like you have injector issues, ohm the injectors and check the reading. Also check / change the 02-sensor. Below is a search which explains how to check the injectors and the required reading for your car.

Hope this helps...............:D



http://forums.corvetteforum.com/sear...archid=6039217

:iagree:

Buy or borrow a fuel pressure gauge and diagnose. It does sound like a leaky injector(s). http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

Thanks for your help. The link you offered on ohming the injectors did not work for me. Can you check it? Perhaps I am doing something wrong. I tend to agree the problem is likely with the injector/s. Just not looking forward to replacing them.

Thanks. I bought a fuel pressure gauge and printed the pdf you sent.
After 30 years of messing with cars looks like I am finally going to have to get involved with fuel injection.

I know the feeling! But after you get involved in F/I it is a LOT easier than any carb. problems you have worked on. Good luck.

I ohm'd the injectors. All were 16.1-16.4. Does that sound right? FP at idle was about 36 psi. Turned the car off and FP went to about 42 psi. After about 35 minutes FP had dropped to about 20 psi. Maybe the leak could be coming from elsewhere, or even the gauge connection but since I am experiencing the rich/flooded condition it's looking like leaking injector(s). Is this a common problem? Looks like a couple of the injectors have already been replaced before I bought the car.
Any and all advice welcome.

The ohms look good. Your fuel pressure looks good and the pressure loss is not crazy, but is leaking somewhere. You need to find the loss area before going any further. http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

Thanks. I read the attached pdf. Seems like a very straight forward approach to detecting a leaking injector. I will do it soon. Since i get a rich condition after is sits, that is what I suspect. Is this somewhat common? Remember, the car sat for 3 years. Also, when I turn the key to "on" should the fuel pump "pump up". It does not do anything until I bump the starter.
BTW. Checked out th pics of your car. Very nice! Besides this '88 I also have a pristine '85 with 14K miles that I have had since '91. I am kind of proud of it. Fortunately I have not had to work on it much. This '88 gives me a chance to learn without "monkeying" with my pride and joy.
Thanks again.

Ohming the injectors just tells what condition the coils are in, the pressure test tells if the injectors, pressure regulator or fuel pump itself is leaking, of course you have to pinch off lines to isolate the area leaking....but, because it floods after shutting it down that points toward injectors, here's another but.....either get a can of SeaFoam or another injector cleaner like Techron and try that before you start leaning toward replacing injectors...you maybe surprised.

I put Techron in it but have not been able to run much through it because the cooling fan did not come on and it started getting hot. So I am also working the cooling fan issue. Do you have any expertise on the fan? I troubleshot it per the Haynes manual and it indicated the relay was bad. But when I bench tested the relay it worked like it should(I think). I will replace the relay anyway and see what happens.
Thanks

I just got my 85 about 2mo ago, had same problems among others and like yours mine had set for awhile. I ohm my injectors and they were bad. During my injector install I change my fuel pressure regulator to an adjustable, but when I pulled the regulator apart on top of the diagram it was full of rust (I guess from condensation from setting) there is no way it was working right. Good luck and ENJOY!! You will get alot of good info from these people!!

BOB

http://members.shaw.ca/corvette86/Co...%20Control.pdf

You my friend are a wealth of information. I appreciate it. Another quick question...Somewhere in my troubleshooting info I read that applying 12 volts to the "G" (I think) terminal of the OBD plug will energize the fuel pump. Do you know if that actually means to run a wire from the pos battery terminal straight to that terminal. Something about that spooks me. I would hate to burn something up.

Get a jumper wire (fused if you like) and connect one end to the positve battery cable and the other end insert into terminal G of the ALDL (lower row, first on bottom). This should send battery voltage to the fuel pump and the pump will run until the wire is removed from the ALDL.

Thanks. I was just a bit nervous about doing that without getting clarification

The fuel pressure will drop after time. They ohm'ed ok. It sounds weird but my coolant temp. sensor was bad and it made the car hard to start and also ran very rich. It was sensing a cold temp. and sending the signal to the computer telling it that it was cold out and needed to richen up the fuel for it to start. Disconnect your wires to the coolant temp. sensor and go to Radio Shack and buy a pack of resistors 3000 ohm and bend it so it will jump the terminals in the connector. It should start and run well for a little bit till it warms up then it will start to run rough again unless you put a lower ohm resistor in it (400) then your coolant temp. sensor is bad. $12 at the parts store. GOOD LUCK Pipe

the car is 20 years old. I would not hesitiate to throw parts at it. that's what I did, and now my car runs great.
IAC, EGR, Injectors, etc, etc.

Thanks. I pulled the fuel rail assembly and found no injectors leaking. I agree the coolant sensor need a look. Sounds like the ECM controls several things based on what it is reading from that sensor. I will aslo be checking the EGR system.