L98 TPI Transplant Issues

Hello all,
I recently purchased a 1972 GMC Jimmmy. The previous owner had transplanted a 350 TPI engine into it from "a late 80's camaro". The guy told us that it had a sporadic starting issue. I'm 99% sure the 350 TPI is from a 1989 camaro since there is no cold-start injector but has VATS. The truck will start up cold without a problem (both in winter and summer). Once it's been warmed up and shut off, it is difficult to restart the engine. After more research it appears the engine isn't switching into closed-loop operation as quickly as it should be. When the engine starts up, it is in open-loop and runs fine. When it finally switches over to closed-loop, engine performance drops and the engine sputters and acts like it wants to die. The only fault code is 15 (low coolant temp). The wires for the coolant temp sensor is fine (checked continuity) so I will try replacing the sensor since it's not a lot of money. However, I don't suspect this is the issue. In manuals I've read, the open-loop uses coolant temp data and PROM numbers to run until engine warms up and switches to closed-loop where the computer can fine tune A/F ratios with the O2 sensor. However, no fault codes appear for the O2 sensor.

I'd greatly appreciate any help or suggestions that can be offered. I hope to get this Jimmy finally running so I can enjoy it all summer with the top off!
Thanks,
Mike  

I also wanted to say that the VATS system was not removed. The previous owner simply put the original lock and key under the dash. I originally thought the VATS system was causing the problem but if it was then it would never start.  

just curious...

you were able to pull codes....    did the connector for the scan tool get installed?????

here is the scan tool values for that engine..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/06/7e/6a/large/0900c15280067e6a.gif

i have not only had problems with the Coolant temp sensor.. but with the pig tail that plugs into it...  i have also had problem on some years where the insulation falls off the wires back in the harness..

by the way... i have replaced the vats system with a 10 turn 1K trimmer pot or a 10K trimmer pot from radio shack..  use the first and second lead or the second and third..  not the first and third..  use a tiny screw driver to match the resistance to the ohm meter reading from the key...


in rereading your post...  i would really want to look at the O2 sensor cross counts... some scan tools can display voltage...  

being in open or closed loop usually does not effect starting..  

does it hold fuel pressure when turned off?????    does the pressure come up as soon as you turn on the key...

remember.. there are 2 ways the electric fuel pump gets powered...

the  fuel pump relay takes orders from the ecm...  when you turn the key on.. it powers the relay for 2 seconds.. if you crank the motor.. the signal from the ignition switch for the starter solenoid is also hooked to the ecm.. look with the scan tool for cranking signal when you are cranking the motor...

the fuel pump also gets power through the 3 wire oil pressure switch...  those also go bad...  switch and pigtails...  

3 wires.. how doe that work..    one wire for the oil pressure gauge or light..  it gets grounded through the switch body...

the outer 2 wires.. usually orange...  one is switched ignition..  usually from the same fuel pump fuse..  the other is to the fuel pump and shares the wire from the fuel pump relay to pump in the tank...

so when the oil pressure comes up .. the isolated switch closes and powers the fuel pump...  

what happened to the air injection system????  is it still there...  smog pump.. diverter valve.. check valves.. tubes into the exhaust manifolds...      any uncommanded air into the exhaust stream upstream of the oxygen sensors will cause the computer to do really weird things to the fuel mixture..

i would also like you to do a voltage drop test..   test the grounds ...   start the motor... turn on the head lights...  digital volt meter to 20 volt scale..    test from the negative battery to the engine block.. less than 0.04 volts is good...

test from the negative battery post to the body...   less than 0,02 volts is good..

test from the engine block to the body...   less than 0,02 volts is good...

if you find more... clean and or replace the  ground wires between those parts..

also double check the grounds for the ECM.. its bolted to the engine somewhere..  usually on the intake... the ecm is only grounded to the engine..  

you might also pull the oxygen sensors..  see if they are clean or gunked up.. do not use spray cleaner..  replace only...  white may be silicone.. yellow coolant....  these motors also had weak intake gaskets.. leak into the rear 2 cylinders.. usually just the number 8...  

I just jumped the two pins on the ALDL which flashed the codes on the SES light. I don't have access to a scan tool. I think the previous owner bought some kind of aftermarket wiring harness to transplant the engine rather than using the harness from the donor camaro. I can see how the coolant temp sensor could cause the no start of the hot engine. The computer uses the sensor at start-up and if the sensor is bad with a hot engine, its probably running too rich at start. However, that still doesn't explain the bad idle once it switches from open-loop to closed-loop operation.

Nice idea with the pot and VATS. Not that anyone would want to steal the beater 72 Jimmy, but the 2nd key is a theft deterrent if removed.  

there are also a few articles on the TPI motor trouble shooting..

http://www.carcraft.com/projectbuild/116_0506_1991_pontiac_firebird_formula_tpi_troubleshooting/index.html


there are 5 or 6 other articles to read... search for TPI in the upper right search window.. then change to performance group after the first search...  

Not sure what happened, I couldn't log into my original account. New name now!

I found a very useful website for TPI installation and troubleshooting here:
http://chevythunder.com/fuel%20injection%20troubleshooting%20pg%20A.htm

Under code 15 it lists a table for CTS readings. At about 70*F it should read 3400 ohms. I measured my CTS and it reads.... 10.5Mohms(10,500,000 ohms)! In the table, the higher the resistance, the lower the temperature, therefore the computer thinks it's like -300*F and therefore probably dumping WAY too much fuel in. Gonna run to Autozone to get a new one ($10.99 isn't a bad price anyway for peace of mind). Also going to see if I can rent an scanner. When I get back I hope to measure fuel pressure. When the key is switched on, the pump primes, but I'm not sure how well it holds.

I'll update when I can get more information.  

Installed the new coolant temp sensor. Trouble code 15 is gone now. It took a while to get the truck started from cold today. Wore the battery down so I had to hook up charger. Once started, the engine seemed to reach closed-loop quicker than before. One it got there though, it still ran rough.

When I switch the ignition on, the fuel pump primes and I get 42 psi. Pressure holds fine. With engine running it sits around 38 psi. I also wasn't sure where to check vacuum, but I connected it to I believe the fuel pressure regulator line since engine RPMs changed when connecting/disconnecting the line. It read 15 in Hg. Idle RPMs were around 600. When I adjusted the screw for a higher idle, the engine smoothed out and idled fine. I went back down to about 500 and it ran really choppy. Turning the headlights on killed the engine so I backed it up to 650 or so.

The bad news is that I haven't fixed the problem. I shut off the engine and immediately restarted it successfully. Then I shut it off again to remove the fuel pressure gauge, tried to restart but it wouldn't go and I still haven't been able to restart it. Another thing I noticed is that before (yesterday and this morning), the oil pressure gauge in the dash would build as I cranked the engine over. Then this afternoon after changing the CTS, it no longer does this. I'm going to check for spark in this "non-starting condition" perhaps its a security issue with VATS that I thought was not a problem.

Any ideas? Thanks,
Mike

Also, the A.I.R. pump is still in place, but it is not hooked up at all.  

Out of pure frustration I just now went outside. The truck fired up first time within a second. Drove it around the block, no problems and no SES. Came back, parked, shut it off. I immediately tried to start it again and, surprise, it started; although it took a little more cranks this time. Ran it for about a minute and shut it off again. Let it sit for about 2 minutes and then tried to restart it. No luck that time. Tried a few more times while letting it sit a few between tries and it never started back up. No fault codes either. Frustration ensued. I also noticed that the oil gauge showed pressure while the engine was running. When I was cranking to try and restart, it'd move but very very little.

Another note; the coolant is boiling. The first time I started it up on Friday the overflow tank spilled over. I think someone had overfilled the radiator. Now it warms up, coolant starts to bubble/boil, steam comes out of the overflow tank, fan kicks on and the steam/boiling stops, fan cuts off and the cycle continues. I feel like the coolant should NOT be boiling.  

Figured I'd post an update on the progress. I followed at tree in a manual for troubleshooting. It's Chart A-3 "Engine Cranks But Won't Run". Fuel, ignition, and SES light were fine. No code 54. Engine had spark. Test light blinked when connected to injector while cranking. Fuel pressure was good. From this point, the chart said to see the "Diagnostic Aids". Plugs weren't fouled. Disconnected MAF sensor with no change. Checked other side of engine's injectors and they blinked when cranking as well.
The only thing left is "An EGR valve sticking open can cause a low A/F ratio during cranking. Unless engine enters "Clear Flood" at the first indication of a flooding condition, it can result in a no start."

To start with this, I took off the air filter and found that the engine fires right up with 2 shots of starting fluid. Without fail I could crank engine with no start, spray 2 shots of starting fluid in and get an immediate engine start, shut it off, crank without start until I added the starting fluid. I'm 99.99$ sure the EGR must be stuck open and letting in too much air.

Now I've got to figure out what exactly I need to do to fix up the EGR system. If this is really the problem that'd be great. Figures its the EGR; they're always clogged/messed up.  

Mike,

Can you tell us more about the "coolant boiling" situation? I would be much more concerned with that and it may mean you are chasing a much larger issue than you suspect. How quickly does the coolant begin to overheat? Does it always do this?

Have you checked timing?  

Also, how do the spark plugs look? Have you changed them?  

Justin,
The truck hasn't been driven in a while due to its unreliability. I think someone put in too much coolant and when the engine heated up, it overflowed out of the overfill tank. It did this once and hasn't done it since because the excess coolant was lost. I'd say the engine ran idle for about 45 minutes before I noticed steam and the initial extra coolant bubbling/boiling out. From then on, the system heats up, steam comes out of the overflow tank (no more drastic boiling/bubbling of the coolant though), electric fan kicks on, steam stops, and then the cycle repeats.

The plugs are good. I had a few of them out last night while running through the diagnosis tree.  

Update

I've driven the truck to work and done some errands in it the past few days and a few more things I've noticed. First, the SES light is very dim when it comes on for a code when the engine is running. But when jumping the diagnostic terminals for checking the codes and etc, the light it just fine and bright. Which leads me to the next thing; I now have a code 33 popping up. It's set when the ECM has seen flow in excess of 45 grams/sec (above about 2.2V) for 1 second when A. engine first starts OR B. TPS is less than 1/4 throttle and RPM is less than 2000.

Could this code be stemming from the (hopefully/probably) stuck-open EGR? My logic being that the engine hunts and idles terribly and perhaps the 33 is being set by the latter condition (< 1/4 TPS and < 2000 RPM). However, the diagnostic flow chart in the manual doesn't mention anything about the EGR. Also note that there are no other codes in the ECM. Nothing about the EGR; that was just deduced from the "Engine Cranks But Won't Run" Chart A-3 when I went through the entire chart and everything checked out except the EGR.

I'm tempted to run through the Code 33 diagnostic chart before I take apart the engine to get to the EGR when I guess I don't know for 100% that it is the problem.

Ideas?  

Further progress...

Cleared the ECM codes to get rid of the 33. Then I couldn't get it to come back after idling engine for about 30 mins and then a short drive. Aggravating. Decided it was a fluke and moved on.

Took the plenum off. The EGR valve was stuck open. I cleaned it out real well and from what I can tell it seems to be working. Upon taking the EGR temp sensor off, I'm not sure if it was already broken or if I broke the wire while taking it off. The wire had been twisted so much in installing/removal that the wire was broken. I fixed that and made sure it was working correctly. The EGR passages weren't clogged up either. Put everything back together and still wouldn't start up. Had to spray some starting fluid in the intake. The idle was still rough. Putting truck into drive/reverse sometimes killed the engine just like before. When cruising at about 50mph and coming to a stop sign, the engine would just about die, same performance as before. Dammit!

Started wondering if it was the idle air control valve. I followed test procedures and it appears to operate as it should. With the truck in neutral, RPMs were about 650. With IAC disconnected, RPSs were about 100RPM lower like manual said. At this state, shifting to drive/reverse kills the engine. I adjusted the screw and now it idles between 1000 and 1500 RPM. Doesn't die when putting it into gear now, however; there's not way it should be idling that high.

To top it off, after my last test drive for the night, I got back and checked codes and had a 21 (TPS voltage too high). I've given up for the night.

This is driving me nuts. Can anyone offer any more suggestions?!

Thanks,
Mike  

mike... i want to know if you spent the few minutes and checked the grounds...

battery to engine..   battery to body..  engine to body... takes less than 2 minutes with the engine running and the head lights on..


how about the ECM connections to the engine.. right out of the ecm harness loom... the ecm is only grounded to the engine..      

how about the dash board grounds...

how about checking the positive side of the battery... to the alternator output terminal with the engine idling..  and with a long long test lead into the car..

partially illuminated lights usually indicate a bad ground...

remember... electrons flow from negative to positive... so if you have a bad ground.. you won't have enough current to supply the circuits properly...

if you have a bad ground...   do to the different loads on the various parts... you may have different voltages on them...     this is a ghost in the system...

there have been racers that used tons of head gasket sealer on their heads..  and one heads spark plugs would not fire... a ground wire between each head and the distributer fixed the problem..

i worry about your bulk head connectors over between the master cylinder and the fender...   how many years have they been there...   they were never really rated for the amount of current that this motor needs to operate properly..    they tend to heat up and burn slightly when heavy loads are involved..   take it apart.. examine it for burning... or do the voltage drop test like i described ... but you will probably need a single long long test lead..  radio shack has bulk wire to make them.  or use a piece of regular wire..


how area the contacts inside your ignition switch..??? i seem to recall that the 72 pick ups still have the key in the dash right.?????/  

i would like to know one think.. the point type ignition switches break the connection for IGN1 when the key is in the crank position...    the same shape ignition switch is used in later model gm trucks that had HEI... the contacts might be larger..   hook a test light to the IGN1 terminal on the back of the ignition switch..  see if you get constant power through the entire cycle from run to start and back...

if your truck has a column mounted ignition switch.. same thing applys..  the replacement later switches ..

where are you located at... somewhere in so cal... where i can drop by with my scanner?????


you might also want to check that the crank signal from the purple wire on the back of the ignition switch is also connected to the proper wire on the ECM harness.. its usually under the dash...  and it does not have to be a thick wire...

and.. the last thing...    for now...    i usually install a mopar starter relay on the heater core box studs...   with a 10 gauge wire running from the top post on the solenoid to the 5/16 stud on the relay..  a 10 gauge wire from the center screwed down terminal to the S terminal on the starter solenoid..    a 14 gauge wire with a ring terminal on one end and a 1/4" push on terminal on the other to shove on one of the push on connectors on the starter relay.. i use a small nut and bolt to connect the 2 ring terminals... so i don't have to cut the factory wires..   the last wire is a 1/4 female push on terminal with a 14 gauge wire to a ring terminal for grounding the starter relay...   i use a starter relay from a 70 dodge dart.. available at most parts stores...

why do this...    it removes 50 to 70 amps of current from having to pass through the electrical system...
the starters kick in almost instantly...  the ignition gets so much better power.. you won't believe the difference.. its like a new car when i get done with this cheep fix...   it removes most of the HOT slow start problems.. as the starter relay now had a very short circuit path to pull the plunger in...



i have only been fixing cars for a living for 30 years.. i sometimes know what i am talking about..   sometimes i say to much.. but i put a ton of info into my posts.. as there are SO many readers that need to absorb this information...