Hello new to the forums. Reaching out to get some assistance with my corvette. It is a 1986 170k miles. the car ran okay previously then Just started having this issue. When attempting to start the car it will start for a second then shut down upon the first attempt of start up. Then it will not attempt to start on additional tries. I checked the fuel pressure at the fuel rail. Turn the key on it jumps to 50 psi to prime the line, Then drops to 15 psi quickly. When turing the car over the fuel pressure stays at 50psi. Once i stop turing the car over fuel pressure drops to 15 psi and slowly drops to 0 psi over the course of 30 minutes. I pinched off the return fuel line and did not get any change in results. I checked spark, I found the spark to be orange in color. The spark plugs I removed were light black on the tips. With the spark plugs this color could they be fouled causing it not to start. Car will not start with starting fluid either.
My thought is the fuel injectors are leaking by causing the spark plugs to foul out? Any assistance would be much appreciated thanks.

 

Never hurts anything except the knuckles to change the plugs.

It could be a faulty pump, but should start with 50PSI during cranking.

Does it sound like the engine is flooding? The ECM has a mode to clear this. If you hold the accelerator down while cranking, it will not cycle the injectors. You could try doing this and see if it leans it out and you get some cylinders to fire. If this is the case, then the injectors are leaking so bad you are flooding the engine. Also, don't forget to check the 9th injector! It is thermostatically controlled on it's own circuit and not by the ECM.

Do you have the ability to read data at the ECM? Another thing to check is the CTS (Coolant Temperature Sensor). If you can see the data make sure it is reading appropriately. Dash gage and ECM use different sensors ( at least I know for sure on the F-Body it does)

Also, Unplug your MAF and try to start. I have hard starting TPIs due to MAF issues.

Always check your basics of timing, vacuum leaks, and any intake leaks upstream of the MAF. This could explain Rich Fouled plugs and running issues slowing getting worse. It will go into limp mode and should be fine to operate to validate it being the culprit - especially if you are all stock.

 

Look at the coolant temp sensor, but the fuel pressure regulator bladder also sounds bad.

 

* I Attempt to start it with the accelerator down. Still no change, unplug the maf , still no start, I don't have the ability to read data off the ecm any suggestions on what I would need to read the ecms data. what methods can i do to troubleshoot the 9th injector. I bought this as a project car and found that there was a mouse nest in the dash, hopefully there isn't a chewed wire causing the no start issue.

 

For reading data: Before I swapped ECMs (My TPI now runs on Dynamic's EBL) I used a Laptop, an USB to ALDL cable from MOATS.net, and both WIN ALDL and Tuner Pro RT. Tuner Pro is better but is a bit more complex to set up.

To own a TPI means you need a scan tool, fuel pressure gage, multimeter, and a set of Torx drivers in your tool box. otherwise you will be just tossing parts.

As mentioned above, your fuel pressure regulator may have failed and is allowing fuel to pass into the manifold. You can pull the vacuum line off and give it a smell. If it has a strong odor of gas or is wet with gas, it could also be causing you problems.

 

repeat the same fp leakdown test but crimp both sending and returning lines just as you shut off the car. i use vice grips with either a good buildup of rag or wrap the jaws in black tape.

see if still leakdown.

also, please pull the vacuum line off the fpr and see if any fuel comes out. it shouldn't.

also, please time how long it takes to bleed fuel pressure off again with both sending and recieving lines crimped.

report back, thnx.

 

Exactly, I usually make a chart and check it at Key off, 1 min, 3 min, 5min, and then every 5 min up to 30 min.

 

UPDATE-Us far as repeating the fuel pressure leak down test as described. Fuel pressure still dropped to 20psi within seconds after cranking the engine over with both return and feed lines crimped with vice grips. Fuel pressure took 30 minutes to drop to zero. So I would think that would indicate leaking fuel injectors? Fuel pressure regulator vent line was dry aNd had no gas odor.
. I replaced the spark plugs all 8 plugs were black as if coated with oil (unsure of plug age). After replacing the plugs it would still not start. I purchased a noid light test kit. I found the noid light to not be flushing but steady on and very dim. Check voltage at the injectors 2vdc. I checked the 2 injector fuses and found them to be corroded and the terminals where the fuse would be pushed into worn out and one side had been pushed into the fuse panel. Tried to repair the existing fuse terminals as best I could and installed new fuses. Crank the car and the noid light now flashes bright. Plug injectors back in now the car starts every time.
. Is there any fix or repair kit for worn out fuse panels. I've had several issues with this fuse panel in this car already.
even tho this ended up being an electrical issue with the injectors, should I still replace them due to the fuel pressure leak down?

 

Nice work Ian. That was some good diagnosis.

As far as replacing injectors, depends on what your plan for the car is. If you are keeping it and plan on driving it all summer, yes i would change them. They are cheap, a set of remanned ones from john at fuel injector connection are very cheap. i put them in my 8) and it made a very big difference.

that said, the work, while easy, is long and arduous the first time. maybe its because i have an issue where if im pulling something apart i have to refurbish it. so i take much longer.

here is my 86 with new injectors. i cleaned/refurbed everything else while doing this.

 

Wow, looks like new...

 

Nice work it looks clean, did you repaint the valve covers?
I'm going to end up changing out the injectors I mind as well clean the motor up aswell.

 

yep. refurbing vc’s to look that good is actually pretty easy if u do it right. mostly time for chemical to strip off paint. inside a tupperware with lid, under a plastic bag used like a blanket. several reapplications of stripper right overtop of all the lifted paint. several! i use the strongest brand i can find.

then i pressure wash them off (local wand wash fine if dont have).

then i sand the remaining paint flat with no lifting edges, there will be lots left surprisingly.

then i wipe with isopropyl alcahol and paper towel, not rags

then i lay sheets of tinfoil on the bbq or oven rack and i bake them at 250 for 15min. then more isopropyl alchahol wiping to remove the oil that always seeps out during baking of the ultra rough casting.

then i a high temp crack fill primer, mist coat.

then i use “aluminum” duplicolor high temp paint

then i use a can of 2k clear and i go EASY so i dont create runs.

also, sounds crazy but i heat the underside of the badge with a heatgun and pry it off, use a combo of small kids paint brushes and toothpicks to restore the color to the badge, then i 2k clear that with the vc’s.

to reapply badge i 80 grit the badge mount area to create tooth, and jb weld it on.

ive skipped the baking before.......and my paint bubbled. lots of debate about the baking being required or not. i never skip it.

done this three times.

for the tpi, simply use eagle1 etching aluminum brightner. if you are in canada its called alumabrite at napa. u have to ask for it.

do not, not, not, waste any time on the tpi without this (or other brand) of aluminum brightner. do not paint the tpi. dont skip out on the intake manifold! your intake manifold bolts will likely be seeping coolant at the rear anyway. here is my 86 finished.



the 86 4+3

the 85 auto

cant find pics of the 87.

the rest of the underhood is just scrub and clean. i dislike this part. but its good as i typicaly find a few “about to fail and leave you on the side of the road” i wrap my looms in magic wrap. it has an appearance of factory loom wrap and with a 10-5% overlap it sticks to itself nice.

i usually push my black fastners into a cardboard box as i go then dust coat them with semi gloss (satin) black tremclad. just a light mist coat. look new.

i had more time in those days. whatever you do, enjoy the process and share the process!

the crevaces on concave depressions in the manifold will come clean. use the etcher. slight and i mean slight agitation helps. even the worst pitted ones come out great.