scoates

A while back I picked up an 87 vette that someone had attempted to convert to carb. I finished the last details needed to get the car running but after a while I decided I wanted to convert it back to TPI.

I picked up a TPI set up and luckily enough the previous owner had left the wiring on the vette. The car will try to start for a second or two but will not stay running.

Here is what I have done so far.
1. Verified spark was good.
2. Verified ground straps are connected.
3. Verified all fuses good in the fuse panel located inside the car.
4. Jumped diagnostic plug with paper clip but it just kept flashing code 12
5. Replaced the control module in the distributor


This is my first TPI setup so I am in unfamiliar territory. I have a Chilton manual and an ohm meter along with various other tools.

I have discovered that the following are missing and do no t know if they would keep the car from starting:
1. Knock sensor
2. EGR solenoid
3. Air diverter valve
4. Air select valve

the original 700r4 transmission has also been swapped out for one that is not computer controlled.


I also pulled the ECM out and opened it up just too see if there was any burned areas in the circuit board and everything looked fine.

redrose

FIRST check with any efi is FUEL PRESSURE...tester under $20 from hf

C409

Did you replace the in-tank fuel pump ?? Carbs run on far less fuel pressure than EFI systems ... PO may have by-passed it altogether electricity-wise . Another thing I have discovered is that used fuel injectors that sit for some time can stick ... have someone crank the engine while you LIGHTLY tap on each injector body with a long dowel rod ... a screwdriver will work but be gentle .... Good Luck!

JackDidley

Around 43# FP is normal for an 87. If the injectors have been sitting around for a long time they could be stuck. If you have fuel pressure at the rail, and no start, you can spray some starting fluid in the throttle body and see if it tries to run.

James93LT1

Get yourself a FSM, it is way more helpful than Chiltons.

Flame Red

I agree with the other poster, to get a carb setup to run they had to do something to reduce the fuel pressure. I bet you are not getting any/enough pressure. Good luck in your quest.

scoates

I have not checked to see what the pressure is set at but I loosened the lines going to the fuel rails to verify the pump is working and it is getting fuel.

To my knowledge the fuel pump in the tank is still original and it was working with the carb. I had to install a bypass regulator in order to get it running with the carb. This was something the previous owner did not realize.

The car tries to run now. It seems to try and run just a hair longer with the starter fluid.

From what I have read the ECM performs checks with various sensor to see if it needs to keep the fuel pump on. If some of the "checks" it looking for are not present then the fuel pump will not stay on.

I think there is something called a noid to check to see if the injectors are getting any current or signal from the ECM. I can't seem to find one locally but I think I can make something from a light bulb to work.

Thanks for the replies so far keep the suggestions coming.

scoates

NEW UPDATE!!

I rigged up a test light and verified that the fuel injector plugs are getting a pulse when trying to crank the car.

After trying for several minutes of off and on cranking I pulled a couple of plugs and could see fuel on them.

Out of frustration I pulled the air filter tube off the throttle body and shot some starter fluid in. My wife was helping me by sitting in the car and turning the key. Still the same thing it would try and start for a split second. For no logical reason I flipped the throttle a couple of times and bam the car started. It continued to run as long as I kept opening the throttle but would try and die if I let off.

It finally died and the battery was too dead to start it anymore so I am letting it set with the battery charger.

Big question is what now?

AGENT 86

What is the throttle position sensor voltage in idle position ?
What is fuel pressure with ignition "on" ?

coupeguy2001

sounds like the idle air is wide open and another vacuum leak such as the brake booster

wingman4rent

Do you have your oil pressure switch/sensors hooked up on the back of the intake, by the distributor? I missed this on my 86 and had to add both, I am not sure what they look like on an 87. Here is an idea what to look for.

Bondami

Oh man does this all sound familiar to me.. Good luck Amigo, I finally gave up and did the carb thing (cleanly and correctly). Not to dissuade you from continuing, By all means carry on. Just be prepared to say "What the Hell did they do that for?" A LOT.. Sometimes the Previous owners tender loving care would have been better off if they had crushed it.

Mine was a wiring botch job, and short of a $1000 replacement loom etc it wasn't going to happen.
But the factory service manual is invaluable, yea Its a $100 dollars for a photocopied service manual but it will make your life Much easier..

383vett

On my 84 I went from the crossfire to a carb to a tpi. It wasn't that difficult but I made all the mods so I could figure out what changes I made. Good luck with your project. As mentioned, do check the fuel pressure, tps setting and timing.

C409

Do you have the correct distributor for the EFI / ECM / ESC ??? You might also check / replace the coolant temp sensor in the front of the intake manifold .

scoates

I cannot seem to get the TPS to the right setting. I thought the TPS might be faulty so I bought new and still no luck. I check the voltage of the gray wire and it is right on 5v however the blue wire only shows .08v. According to chevythunder the blue wire should have .54 volts.

I am also getting a code 42 now. This is "Electronic Spark Timing (EST) circuit grounded or Ignition Control (IC) circuit grounded or faulty bypass line.

I have not checked the actual fuel pressure yet only verified that it is getting fuel pressure.

I still need to check the idle air but I believe I have all vacuum ports capped or hooked to something. the break booster is hooked up correctly and was working before with no issues.

They are not exactly the same on the 87 but both are hooked up.

Yeah I have said that a lot already but I am bound and determined to get the TPI working. I can't pass emissions and the resell value would probably be pretty low if I decided to ever sell. I also could not get the carb to stop boiling the fuel out of the fuel bowl in this hot Texas heat. Where can I get the service manual from?

Thanks for the encouragement. I am confident I will get it sorted out eventually.

I did not verify the P/N on the distributor but bought it from a local guy that only deals in used corvette parts. He specializes in C4 parts. I also checked autozone and the same distributor is listed for 85-91 give or take a year. I did the research before I actually bought it just can't remember the exact years off the top of my head.

And just a recap the car will start now as long as I crack the throttle open and if I keep feather it, the car will continue to run. I does however run extremely rough. It also get the code 42 now.

JackDidley

It sounds like the throttle blades are all the way closed. Take a Torx bit and screw in the idle screw on the throttle body while watching the volt guage on the TPS. See if it will go up to .54.

AGENT 86

Are you measuring the TPS voltage with the connector attached to sensor and your probes measuring the top 2 wires ? I slide my probes into the backside of connector, until they reach the metal part. The I rock the sensor front/back until I get the correct voltage and tighten down sensor screws.
http://members.shaw.ca/corvette86/Code%2022.pdf

Code 42 code be as simple as the timing bypass connector being unplugged. Single tan wire with black stripe, the connector should be beside booster(engine side).
http://members.shaw.ca/corvette86/Code%2042.pdf

NXS

If it was mine I knew nothing about it, ie starting from scratch here is what I would do.
(I know you already did some of this)
Check spark, make sure it is able to jump 3/4" and continue for several revolutions.

if that checks, 2nd (as noted) check the fuel pressure. on a TBI system low pressure will make one act like it's flooding and roll black smoke.
If the pressure is 40-45 lbs.

Get a noid light like you said make sure the injectors stay firing for several revolutions.
if they do not fire at all you need to be checking your fuses and relays.
if they fire then stop look into the fuel pump/oil pressure safety circuit (as already noted)

if they do fire for several revolutions check for bad gas. this new gas they are selling now seems to have no shelf life. The vette in my avatar had this very problem (and did exactly as you say, fouled plugs try to start but no go), bad gas, I had to drain the tank and flush the lines, it fired right up.

scoates

OK apparently I had a brain fart. I had been checking the resistance on the TPS rather than the voltage. Checked it the correct way and it shows .53v with the connector plugged up. I can roll the throttle and the voltage goes up.

It also seems that the battery is loosing its charge. I am going to recharge it and see if looses the charge with it disconnected from the car. If it doesn't I will connect it and let it sit and check whether it discharges once hooked up to the car.

scoates

I have taken everyone's advice and ordered a factory service manual. I hope it gets here by the end of the week. I have also found a noid light set locally so I will pick that up in a few days. FYI here in Houston area Advanced Auto Parts carry the noid light set for around $21. They are the only ones I found with them in stock.