350 5.7 TBI Timing/Fuel Issue

[Jeepcrazed]

I've been off-roading for over 20 years and had several modified Jeeps with various motors. I recently purchased a Jeep CJ7 that already had a 1993 Chevy C1500 TBI 5.7 motor in it. Guy who had it wheeled all over the Southeast and out West. He let it sit in his basement for a couple years due to his work travel schedule. He decided to sell and went to fire it up. It would idle fine but he couldn't even drive it up the driveway (on a hill) as it would stall when you gave it gas. Now you could rev the motor all you want sitting still but once in gear (it's a manual - SM465) and gave it gas it had no power.

I pulled the trigger and bought it at a discounted price. I got it home and replaced the fuel filter (it was pretty dirty!). It ran better but still had power issues and would throw a Code 42. I replaced the EST circuit and ignition module. No change. Played with the motor for several weeks with new injectors, map sensor, IAC, fuel regulator, TBI rebuild, knock sensor. Checked all wires for open loop, bad ground. Added more engine grounds (body to frame, body to battery, frame to battery, etc). Forgot to mention, the timing was checked (set to 0 with bypass wire disconnected) I replaced the computer (16146299). Transferred the AWLB chip to the new computer. (There is not catalytic converter and muffler was taken off and run to see if there was an obstruction in it as well.) A couple weeks ago I went for a test drive in the neighborhood and all of a sudden I had POWER! The throttle had a lull in it but it would GO! Ocassionally it sputtered when I got on the throttle but would get it. The next few days it went right back to normal. NO POWER.

I broke down and took to a mechanic. He was stumped. He said the best he could get it to run was disconnecting the bypass wire and advancing the timing (basically eliminating the computer control).

Since I planned on do a major overhaul on the Jeep I began tear-down. I pulled the cage, built a new dash with all new auto-meter gauges, put in new fuel cell (along with all new fuel lines), new carter p5001 fuel pump, new crate motor from Summit (replaced with same motor, stock 5.7 TBI) and installed a Painless wire harness (wanted to eliminate any wire issues). I even got a new eprom and installed it just in case the old one had gone bad. I have a fuel pressure gauge on the back of the TBI (supply side of course) and it stays at 12 PSI. I tried an adjustable FPR, but turned all the way down it was at 14-15. The motor is running rich.

Like I said before it will start right up and idle (even though it doesn't sound like a healthy idle) but when you try to drive it, no power. It will also backfire through the exhaust when you give it quick throttle. Painless calls for using the 1227747 ECM, with ASDU eprom and 16060836 calpak. I have the ECM and eprom and I'm waiting on the calpak to come in the mail. I'm gonna try the new computer/chips and keep my fingers crossed but doubtful.

Any reccommendations?

[1project2many]

Hey! Stop deleting posts!!! lol... I just got done moving the other thread. :laugh:

You've changed so many parts that you should be looking at the few that have been re-used. Is it possible that the distributor cap to rotor phasing is off and the wrong cylinder is receiving spark? Or maybe there's a problem with the coil? Is the distributor wiring laying on plug wiring anywhere? Is the pickup coil correct for the module (there are clockwise and CCW parts)? Did you re-use the balancer? Is it possible the outer ring is no longer in the correct position? Or is the balancer designed for a different timing cover and the mark is not lining up at TDC?

You should have tools to monitor what the computer is seeing and commanding. A scantool or a laptop with scan software and a cable will work. Check timing at the balancer against what the ecm is commanding. A simple spark test tool can give good indication if spark is constant and steady. Confirm the throttle body and injectors are correct for the engine displacement. If there's an EGR make sure it is not opening (this usually gives a sag without backfire, but it helps to check everything). It can be really tough to diagnose a vehicle over the 'net but sometimes with enough patience and persistence it can be done.

[Jeepcrazed]

Hey! Stop deleting posts!!! lol... I just got done moving the other thread. :laugh:

You've changed so many parts that you should be looking at the few that have been re-used. Is it possible that the distributor cap to rotor phasing is off and the wrong cylinder is receiving spark? Or maybe there's a problem with the coil? Is the distributor wiring laying on plug wiring anywhere? Is the pickup coil correct for the module (there are clockwise and CCW parts)? Did you re-use the balancer? Is it possible the outer ring is no longer in the correct position? Or is the balancer designed for a different timing cover and the mark is not lining up at TDC?

You should have tools to monitor what the computer is seeing and commanding. A scantool or a laptop with scan software and a cable will work. Check timing at the balancer against what the ecm is commanding. A simple spark test tool can give good indication if spark is constant and steady. Confirm the throttle body and injectors are correct for the engine displacement. If there's an EGR make sure it is not opening (this usually gives a sag without backfire, but it helps to check everything). It can be really tough to diagnose a vehicle over the 'net but sometimes with enough patience and persistence it can be done.

Sorry for the confusion and thanks for cleaning up my mess! I should have elaborated a little further. This was a new long block and ALL sensors have been replaced with new ones, new injectors, dizzy, plugs, wires, EGR, etc. The only thing not "new" is the TBI assmebly (even though I've cleaned it twice to ensure it's good to go). I'll have to look into where to pick up a scantool or a cable/software to monitor with the laptop.

[1project2many]

No problem. We try to be low-stress here.

Well, you just eliminated a bunch more variables. You can use a timing light to watch the pattern from the injectors to ensure they're both firing consistently. You can also look at the top of the injectors under the electrical connector to see if the colored stripes are still visible (probably not). The stripes can be used to identify the injectors.

If you want an all new TB, I just found a kewl site two days ago...
http://www.oem-surplus.com/gmwp/gmc.htm

If you can find a TB that will fit your application you can't beat the prices.

[Jeepcrazed]

Already checked the injectors. All is good there. Just ordered a scantool. Should be here on Saturday. Thanks for the help so far!

[1project2many]

With so many parts replaced, and confidence that all the parts are good, it's gonna be tough. Plug wire routing can cause crossfire which pops n snorts. Swapping 5 n 7 wires is one of the most common SBC mistakes and it also causes pops n snaps. It can be hard to confirm injectors are truly good without specialized equipment although it is sometimes possible to rule out some very obvious problems. Are you using a 4bbl manifold and spacer under the TB? If so then a stock tune is not likely to work there. Auto trans calibrations on early ecm's are usually very different from manual and can cause driveability issues. If it were me I'd be watching spark with a scope, checking timing against commanded using a light, checking other scan tool values and comparing them to expected readings, and I'd be trying to watch mixture for signs of lean / rich using O2 readings.

[ony]

check the ignition module in the dist. I think the green pick up wire goes to the in side close to the dist shaft. some time when the connector breaks these wires get reversed. if the connector is broken.

[Jeepcrazed]

With so many parts replaced, and confidence that all the parts are good, it's gonna be tough. Plug wire routing can cause crossfire which pops n snorts. Swapping 5 n 7 wires is one of the most common SBC mistakes and it also causes pops n snaps. It can be hard to confirm injectors are truly good without specialized equipment although it is sometimes possible to rule out some very obvious problems. Are you using a 4bbl manifold and spacer under the TB? If so then a stock tune is not likely to work there. Auto trans calibrations on early ecm's are usually very different from manual and can cause driveability issues. If it were me I'd be watching spark with a scope, checking timing against commanded using a light, checking other scan tool values and comparing them to expected readings, and I'd be trying to watch mixture for signs of lean / rich using O2 readings.

Thanks for the insight 1project2many! I hope to shed some light on things when my scantool comes in tomorrow (and I learn how to use it).

[Jeepcrazed]

check the ignition module in the dist. I think the green pick up wire goes to the in side close to the dist shaft. some time when the connector breaks these wires get reversed. if the connector is broken.
Thanks Ony! I first replaced the ignition module in the old motor to no avail and since have dropped in a new distributor, which I reused in the new motor.

[1project2many]

How's this going? Any luck?

Does the engine have any problems when the vehicle is stationary? Is the popping when the throttle's opened present when the vehicle is stationary? Were you able to watch the fuel pressure gauge while driving?

[Jeepcrazed]

I have a scan tool but didn't realize because it's an OBD1 I can't look at live data or freeze frame. It idles fine. As soon as you give it throttle in a stationary position, you can hear the time/fuel mixture isn't right. As you give it a quick rev to about 3K and let off, I can get it to backfire through the exhaust. When I try to drive it, it has no power (it's like the computer isn't adjusting the timing). It will backfire between shifts. I broke down again and drove it to a shop nearby yesterday. What's weird is under very light throttle, it's started coming alive and taking off with a great deal of power. The popping I mentioned is when it starts to do this and I give it more throttle. It kinda of sputters. I have a couple different carter fuel pumps I've tried. One is the 4601HP. This is what the original owner had in it, I just put in a new one. The other is the P5001. Don't see a difference in performance between them. The P5001 has more pressure than the 4601HP. If I leave the FPR where it's set (I have the adjustable one in it right now) with the 4601HP it runs at 10-11 PSI. If I swap in the P5001 it runs about 13-14 PSI. This is only a stock motor with no upgrades. Spray pattern looks good with the timing light. Injectors are new.

[1project2many]

Interesting.

I did have similar issues years ago tuning a Jeep that had a non-baffled carbureted tank. I tuned it on the dyno and had tons of power but as soon as I started to accelerate it had some real issues.

Are you tuning with a full tank? Maybe you can monitor fuel pressure while accelerating? Zip tie a cell phone to take a movie of the pressure gauge as you accelerate??

Popping on decel could easily be due to slightly excess fuel. If the engine is going lean due during acceleration then it could be adding fuel, which, if it's due to fuel slosh, could lead to the exhaust being overly rich on decel.

If you have a scantool that will communicate with the ecm, you will see live data that will update at a very slow rate.

[Jeepcrazed]

I don't have a oil pressure switch installed. Would this cause any of my issues?

[1project2many]

It should not cause an issue. The oil pressure switch and the fuel pump relay can both power the pump independently. I've been driving my '57 without an oil pressure switch since I built it in '92.

[Jeepcrazed]

The mechanic I took it to says I should have it. Called Painless since I have their harness and he swears I NEED it. I guess I'll pick one up and throw it on. Mechanic also said my fuel pressure was way low so I put the TBI pump back on and cranked up the pressure at my FPR. We'll see what happens when I install the switch but I don't think it will do much.

[fastacton]

I delete the oil pressure switch connector on every harness I build and I've built a couple of hundred without any issues. Whoever you talked to at Painless has no idea what they're talking about (I also have one of their harnesses and it works fine with out it as well). The switch is wired in parallel with the fuel pump relay, so as long as the relay is working properly, the switch has no effect. I wouldn't even waste your time on it. If you really want to test the difference, just jumper the switch connector (make sure you can disconnect quickly as you don't want the fuel pump to keep running if there are problems).

[Fast355]

I delete the oil pressure switch connector on every harness I build and I've built a couple of hundred without any issues. Whoever you talked to at Painless has no idea what they're talking about (I also have one of their harnesses and it works fine with out it as well). The switch is wired in parallel with the fuel pump relay, so as long as the relay is working properly, the switch has no effect. I wouldn't even waste your time on it. If you really want to test the difference, just jumper the switch connector (make sure you can disconnect quickly as you don't want the fuel pump to keep running if there are problems).

I prefer to keep the oil pressure switch. The engine only NEEDS one or the other but the 2nd is redundancy.

[1project2many]

Called Painless since I have their harness and he swears I NEED it.

I certainly understand wanting to remove all the variables but the switch is not necessary. If you NEEDED the switch then the vehicle would not run without it. It does not provide any signal to the ecm. It's a switch to power the pump in addition to the relay. There is some argument that the relay contacts can bounce while driving and eventually the contacts can become pitted due to the current through the pump. The argument is that when it happens the pump can stop working and the engine will stall, or the relay will stick "on" and the pump will run after the engine is off. This, I've been told, is part of the reason GM included the oil pressure switch. I don't disagree with having a redundant switch, but it doesn't seem as necessary when you consider there are no other redundant components on the engine. When I built my harness I used only the relay but ran a wire to the battery with a connector. If the relay ever fails I can connect the pump manually.

[Jeepcrazed]

I agree, the switch is not going to make a difference. I threw it on anyway and swapped out my fuel pump back to the carter p5001 tbi pump. Adjusted my fuel pressure up (he recommended 20 psi - seems way to high!). I cleared the codes and warmed up the motor. I can still hear that it doesn't run smooth. Anyway, I hooked up my scan tool. These are the codes it's throwing:

13, 14, 23, 25, 33, 43, 51

I have a new A1-Cardone ECM 122747, new ASDU prom and new cal-pak 16060836 (these are all the items painless wants you to run with this harness) I'm leaning toward I have a bad ECM but concerned that because I have a manual, should I use a different PROM? Even at idle, I can tell it's not running right and throwing all these codes even before I try and drive it down the road.

I tried to drive it in the neighborhood today. Still no power, backfires between gears (when I let it get to 2500 or so between shifts). Still seems like computer isn't communicating with the sensors correctly. Anyone have any ideas? All I have is an OBD1 port.

I did re-test the MAP sensor again today. It checks out fine. Vacuum good to map sensor as well. I'm about to buy an A/C Delco computer and see if there's a difference.

[1project2many]

There's a pretty significant issue if you're seeing all those codes. 13 is O2 sensor insufficient activity. 14 is CTS high. 23 is manifold air temp sensor low. In most applications the 7747 is not equipped with a manifold air temp sensor. 25 is manifold air temp sensor high. Very uncommon to see both high and low sensor codes in the same application, but worse yet, the 7747 application (as mentioned) does not usually get paired with MAT sensor. 33 is a MAP sensor code, MAP voltage high. This code can be set if the IAC is all the way open trying to keep the engine running. 43 is knock signal present when it should't be, or not present when it's expected. 51 is a prom error. That's the bad one.

Ultimately you have a list of codes that really shouldn't be present. First, you need to ensure the large ASDU chip is installed correctly and none of the legs are bent. If its been installed backward it could be no good as the older TTL chips don't put up with reversal. They also don't tolerate shocks from static electricity. Ask me how I know. The simple test to check whether or not the ecm thinks the chip is good is to turn the key off for 30 seconds or more, turn the key on, and watch the check engine light. The light should illuminate for a few seconds, go out for a few seconds, then turn on and stay on. Any other behavior like a rapidly flashing light or the light turning on immediately and staying on indicates a problem. This test is only accurate after they key has been off for at least 30 seconds. There is absolutely no sense in chasing any other issues until the ecm and memcal play nice together and code 51 is not present.

The eprom has a notch in the end. The eprom holder has a notch in the end. The notches must line up. Confirm alignment and condition of the legs. If all is well then you will either need another ecm or another chip, or both. Do you still have the original ecm and matching chip? You could plug the ecm into the harness and check for codes as a diagnostic tool. You can also get codes by jumpering pins A and B in the ALDL connector and watching the check engine light, just to confirm the scantool is reading codes accurately.

[buddrow]

Start with the really simple stuff and verify the grounds are hooked up. Poor or missing sensor grounds can cause all sorts of issues.

Buddrow

[Jeepcrazed]

I appreciate the comments/suggestions! I swapped out to another new computer (gotta love warranty coverage). Power is back!!

[1project2many]

Excellent news! Now are you going to attempt your own tuning?

[Jeepcrazed]

I've got several other things to work on first to get ready for a ride in a few weeks in Knoxville. I may come back to it and see what improvements can be made.

[Jeepcrazed]

Jeep did great on the ride in Knoxville. Funny thing is, when I hook up my scan tool to check for codes, I'm still seeing several codes (O2, map, IAC, ECM, etc...) but it's running just fine and not turning on the warning light. I'm going to pull the plugs and see what they tell me.

[1project2many]

Does the light work? I've seen them burn out before.

[jim_in_dorris]

High and low voltage codes for the same sensor makes me think there is a ground problem. Perhaps a big 3 upgrade is in order. It is amazing what it did for my truck.

[Jeepcrazed]

Light is good. Just a reminder, this is a brand new painless harness. I have the battery grounded to the engine. The engine is grounded to the frame and the frame is grounded to the tub. Alternator has large gauge wire straight to battery. I appreciate the input, keep those ideas coming! Forgot to mention, pulled the plugs. Too much carbon build up. Appears to be running rich.

[jim_in_dorris]

All the error codes are most likely the reason for rich running. I know the sensors are new. I also understand the wiring harness is new. There are 4 reasons (generally) that sensor error codes are set. 1. Sensor bad. Even new ones can be bad, but not usually all at the same time. 2. The reference voltage is too high or to low. 3 the ground is not zero volts. And 4. The sensors are all good, your voltages are correct, and your motor has a serious problem. A TunerproRT log file will show what is going on.

[1project2many]

Light is good. Just a reminder, this is a brand new painless harness. I have the battery grounded to the engine. The engine is grounded to the frame and the frame is grounded to the tub. Alternator has large gauge wire straight to battery. I appreciate the input, keep those ideas coming! Forgot to mention, pulled the plugs. Too much carbon build up. Appears to be running rich.

Then the codes are most likely from history and not current. Clear them and see what comes back.

[jim_in_dorris]

1project, he swapped out computers between getting codes, that will have cleared them. If they continue to come back he has a problem

[1project2many]

Ok, but he took a long drive after the swap? With no light, but it set codes? If a code is present there should be a check engine light. And it runs fine but it's too rich?? This is a strange excercise in contradictions.

[jim_in_dorris]

Exactly. I don't remember, but I believe if a code is intermittent, it is possible for them to be set without turning on the cel. It has been a while, but I believe that to be the case. If so, intermittent codes being set will be caused by floating grounds or fluxuating reference voltages. Something as simple as a ground wire that isn't making contact with bare metal. Some people have had problems if the ground strap between the passenger side head and the body is missing. Without being there, it is really difficult to make a diagnosis. I really hope that when this gets figured out it is posted on the thread.

[Jeepcrazed]

I'm gonna work on it when I get off work today and see what I can find out. I will definitely post whatever the problem ends up being. Only way I know to clear codes is to disconnect battery for a couple minutes. My scanner won't allow me to clear the codes. Thanks again everyone for your input!!