JVince

I transferred the PROM out of the bad ECM and into the new one. I also spent a few hours checking for shorts in the plugs that feed the ECM, everything looked good. With the key off I only had one 12v input, with the key on I found several, but nothing that looked like an short or grounded connection. I unhooked the battery and plugged in the new ECM, then grounded the A and B ports to check the codes. No SES light at all. I've yet to see the SES flash, or turn on at any time regardless of AB Diagnostics or without. The only idiot lights I get are "fasten belts", "brake" and one flash of the security light.

If I've understood correctly, even if there are no codes stored I should get a "12" flashed with AB connected. And if all is well I'm thinking I would still see the SES if I try to crank the car normally. I still don't. Could the PROM I pulled from the old unit be bad? Could JUST the SES light bulb have blown? Once again, the motor turns over and will fire if I drop fuel or carb cleaner in the TBI. Just no power to the injectors still. I have the bypass for the VATS ready to install, but I was hoping to see some codes before I went that route. Any ideas? Thanks again!

9manastacio

iTrader: (4)

I had that problem on my tpi when i swapped it into my v6 bird. I tried a different ecm and that didnt help, try unplugging the connectors at the comp, putting dialectric grease on the connector and then plugging it in solid. make dure all connectors are tight, including c207. I had this keep happening and the injectors would not get 12v. I took out the ecm, blew it off with air inside,incase there was a moisture problem, and made sure all connections were good, and i havent had this problem in several months. just check everything!

9manastacio

iTrader: (4)

You have VATS i take it?

JVince

Yes, VATS. Since the motor turns over the starter is obviously working. I have the VATS bypass module that should send the signal to the ECM to pulse the injectors, but I was hoping to get some engine trouble codes before that. I've recently been told that there's a fuseable link coming off the starter that can cause power issues to the ECM. I'll try cleaning off the connections and making sure it's all tight.

I have to look up the c207 though. I honestly have no idea what that is

*edit* I found some pics of those connectors, checking them now. If there are fuseable links in these I will check them as well. I know the ECM is getting power but no SES light yet. Also checking for a pulled bulb (that would be nice!).

*edit part 2* I wasn't able to get the speedo cable disconnected in order to remove the gauge cluster to check the bulb, but I did find a wire pulled loose from a clip way up under the steering column. I reattached it temporarily and it cured an odd short in the gauges (when you used the dimmer, the volt gauge went to 0 and the RPM gauge went to 4500, fun one!). Still no luck with getting the SES to light up. That's the only non working bulb right now.

I'll probably go ahead and remove the cluster just to double check the bulb since I'm this far, but I'm thinking there must be something else keeping the ECM from "booting" up?

I also found an hanging clip under the dash, unidentified even after a little looking. Here's the pic:

antoine

Have you checked the fuse by the battery if its blown you will not have a check engine light.

JVince

I have not. Is that a fuseable link? I'll poke around the battery to see if I can locate it.

ASE doc

The fuse by the battery is the FI fuse. It provides batt power to the ECM and the fuel pump. You should have constant 12v to pins B1 & C16 at the ECM. Do you have a wiring diagram for this car? If you dont you need to get one. Otherwise youre stabbing in the dark. I can point out circuits to check but if you dont have good diagrams, it does no good.

JVince

I have the Haynes manual diagrams for now. They're helpful but not as detailed as I'd like. Most of my previous hobby work has been on old muscle cars so my wiring experience has been limited. Of course I work in the IT field so I have a basic understanding .

I didn't notice a fuse near the battery but I honestly wasn't looking. It would be an early birthday present if it brought my ECM to life and started throwing codes at me.

I can't verify the pins but I did get constant 12v at the ecm. I think at only one pin when the key was turned off but I'd have to check my notes.

JVince

My wife just called to inform me the that fuse by the battery was indeed blown. She unhooked the battery, replaced the fuse, reconnected the battery and turned the key. We got a "12" code only. I assume since the ECM is brand new it won't generate a real code until we try to crank the car (I told her NOT to crank it till I get home ).

JPalumbo89

Yes indeed she threw 1 long, 2 short codes after changing that fuse.
(Yes Dear, I'll wait until you get home to fiddle with her more!)

JVince

Hey, that's my wife . Can you tell she's excited about getting the Camaro running? I'm going to do a few more checks this afternoon but if all goes well I'll try to crank her up and see what happens. At least the SES works now!

ASE doc

Id say things look very good for you. Let us know how it runs.

JVince

Well we're making progress but not running yet. I cranked the motor a few times but we're still not getting fuel. I should be able to see the squirts into the TB right? I can hear what sounds like compression pops while cranking. Still no codes other than the three "12s" after about five crank tries. I'm going to check the dark blue fuel signal wire on the ECM next. Can I do that with the ECM removed? I already have the VATS bypass module you guys linked for me ready to install. If I'm not getting a fuel signal reading from that blue wire I'll probably install that next.

I noticed too that I can't seem to hear the fuel pump priming. It should prime a bit when you turn the key (not to crank position) correct?

We can't thank you guys enough. My wife is crazy excited that we're making headway and that her new toy may be running soon!

ASE doc

You should hear the fuel pump run. The VATS prevents fueling by disabling injector pulse. It doesn't prevent fuel pump operation. Find out why your fuel pump isn't running. A shorted winding in the pump would explain the blown FI fuse. Pefform this quick test: Use a screwdriver with the tip resting on an injector and the handle held against your ear, to listen for injector "click" while cranking the engine. If no click, proceed with VATS testing and bypass, if needed.

If you get "click", test fuel pump by grounding the green and white wire at the fuel pump relay. With a grounded test lead connected to this circuit, the pump should run. Carefully loosen the pressure line(larger of the two) at the TB to check for pressure while performing the fuel pump test.

Note: use a 3/4 wrench to hold the fitting while using a 5/8 wrench to loosen the flair nut. This prevents twisting the steel line.

You should test for fuel enable signal with the ECM installed. Look for the 5v signal on the drk blu wire to drop to about 3 volts on your DVOM, when you try to start engine.

JVince

Ahhh, the old school stethoscope trick! I've used that to find valve ticks through headers. The starter motor is fairly loud so hopefully I can hear those clicks (if the injectors are firing). It should be a repeating pattern correct? I was going to check for voltage at the injectors also.

Could I put 12v to the G terminal of the ALDL to run the FP? Testing for fuel pressure at the TB was on my list also

The wiring diagram I'm looking at for the ECM shows more than one dark blue wire. I believe the correct terminal was B6, but my diagram doesn't indicate which that is. If this diagram is correct the "pass-key decoder module" drk blue wire should be between a tan/blk and a pink/blk wire. Of course that's from a 91 5.0 TBI diagram so I'm not 100% on the accuracy...

ASE doc

You should really invest in the factory manual for your car. It's published by Helm's publishing and i believe you can order it online. They run about $100 so be prepared but it's absolutely priceless to you.

Generally, I use either a stethiscope, noid lights, or lab scope for testing injector pulse. I just gave you the screwdriver trick because it doesn't require any special tools. If you have trouble hearing the injectors, buy a stethiscope. They're fairly cheap. Noids are cheap too.

Yes, terminal G of the ALDL will work to test the pump. I'm old and I forget these things. B6 appears to be correct for the fuel enable circuit. It's between a blk and a ppl/wht(according to Mitchell). Connector B is a 12 pin connector. Look closely with a bright light and magnifying glass for the letter B on the connector body.

JVince

I'm going to check out Helms now. I've always preferred the shop manuals but the car came with two Haynes so I've been working off those and diagrams I've found online.

I'm almost certain I have a noid light somewhere. I totally forgot about it till you mentioned it, thanks! I've been working on an old carb car too long .

I have a nice list of things for us to try when I get home today, I'll be sure to keep everyone updated. We'll see if we can get some pictures up as well. Thanks again!

I didn't even realize the circuits were labeled on the ECM. I guess I'm old too.

ASE doc

The circuits aren't exactly labeled. The connectors have the connector letter and pin numbers embossed in the plastic. Very small carracters, that's why the bright light and magnifying glass.

JVince

So I got pulses from both injector connections via noid light. I put 12v to the G circuit on the ALDL, no sound at all. I removed the driver side fuel inlet to the TB and had my wife crank the motor, no fuel. I'm starting to think fuel pump but I want to make sure there's nothing else I can check before I buy one. I think the TBI also has the pump in the gas tank (I didn't see it on the lower part of the motor) so I'd like to save dropping the tank till last

Just to double check, here's the inlet I removed. I didn't think it would matter which side.



Could it be a FP relay? Is there another sneaky fuse I may have missed?

I did get to give my wife a treat by spraying starter fluid into the TB and letting her fire up the motor for a few seconds. That was fun.

*edit* I didn't continue with testing voltage at the ECM since it seems the VATS and ECM are indeed working as intended. I'm hanging on to that bypass module though

JVince

I just heard from my brother in law that he replaced the fuel pump with a new unit about 3 months ago. I don't know if he did the filter or screen, but I've heard you can screw up a new pump if you're not careful. Regardless I'm guessing there are other things I can test before going that route again.

ASE doc

The fuse you replaced is the only fuse protecting the fuel pump.

Test for power from the fuel pump relay, tan/wht wire. There is a connector under the car, just in front and above the tank(C313). I rarely find issues in the fuel pump wiring but if you really want to be certain, you can test for power and ground there. Be sure to check both because a bad ground will prevent the pump working just as well as no power. There are a few connections between the relay and the pump. One is connector C207(pin D), it's central to the ECM wiring and you can check there too. Another is C208. It's similar to C207 but on the left side of the dash. From C208(pin P), the fuel pump wiring runs to the rear of the car, under the carpet, to C313.

JVince

If I get power at the relay and at C313 I may just proceed to pulling the pump. We just put gas in too, hehe.

ASE doc

I made an extraction pump using a Carter inline pump and an empty 20gal drum. I have a long peice of poly fuel line(the hard plastic kind) that can be fed down through the fill tube. I use it to empty a fuel tank before dropping it. It's common for people to fill their tank when their fuel pump fails. They often think they're just out of gas, like their gauge lies to them.

You will not have an easy time managing a full tank of gas. Any way you can find to drain the fuel would be good. Maybe syphon it? If you can get a hose down the fill tube. I know that's tough though. In a pinch, you can lower the tank, remove the intank unit, and syphon the fuel out through the open hole. This way you will atleast have an empty tank to reinstall.

One thing about dropping the 3rd gen tank, remove the rear exhaust before you even try to pull the tank. So many rookies think they'll somehow get around it and unstrap the tank only to end up with a mess on their hands. The tank will not come out with the muffler in place, even if you lower the exhaust as far as it will go. You need to unbolt the flange behind the cat, unbolt the hangers at the muffler and extract the exhaust before you start on the tank.

I have been able on some to leave the exhaust hanging over the axle while I R & R'd the tank but this is on a Rotary lift, not on jack stands.

ASE doc

BTW, the two wire connector in the photo above may go to the vehicle speed sensor. It could also be to the brake switch for the TCC lockup. My diagrams for your car are incomplete. How did you do with Helm's?

Edit: I just looked at Helm's online. Guess the prices have gone up a little. Hehehe. Still, even at $150, it's worth every penny. The Electrical Diagnosis Suppliment that comes with it would be worth it's weight in gold to you right now.

JVince

Yep, my brother in law mentioned that he had to remove the rear exhaust when he dropped the tank to replace the pump. I think I can rig something up to empty the tank, even if it's the old school syphon trick.
Do the FP relays fail often? I'm hoping that it's just a bad relay. Easy and cheap to fix.
I did check out Helms yesterday and noticed the price . Not a bad investment really, and most shop manuals I've bought (only a handful) haven't been cheap. I was happy to see that it came with that extra diagnosis supplement. What's interesting is that the TWO Haynes manuals I have (one old, one new) have different wiring diagrams. Both are in agreement with each other, but where one is lacking the other seems to pick up. Happy accident I suppose.
One other thing I plan on checking today is the other fuel line to the throttle body. I thought both were inlet lines (too much dbl pump carb work!) so I only removed one. I think it was the inlet but I'm checking the other just in case I pulled the return line

JVince

*Update*
It looks like the FP relay has been replaced. I get 12v on tan/wht and red. That looks to be the pass through fuel circuit, so I moved to the connection near the tank. That must be the c313. It's a three pin connector and sits above the tank, with a wire leading to the top of the tank and FP. With the key on I only got 7.9v from the purple wire, none from blk or grey. I didn't check with the motor cranking.

7.9v seems strange so I tested it a few times yielding the same results. I assume the blk on the connection is ground and maybe the grey is for when the engine is running? I couldn't find it on the wiring diagram I found off a link here (which has been very useful so far).

If those results sound correct I'll proceed to siphoning out the gas and dropping the tank. Honestly the 7.9 v at the C313 worries me a bit.

*edit*
After more reading it looks like the purple wire on the C313 should be 12v and the gray is the sending unit signal back to the fuel gauge (maybe vice vs.) We noticed that when we added 5 gallons of fuel the gauge went to all Full (from E). I'm starting to think there might be a short between the FP relay and the C313, or SOMETHING that is causing resistance.

JVince

I couldn't stand it so I went outside and played with the wires some more. The ground at C313 checks out. I tried multiple ground sources for the 12v wire and I still get 7.9v. On a hunch I loosened the fuel filter lines and tried cranking the car to look for spurts of fuel. Nothing. I banged a bit on the tank to see if the pump was jammed up. No dice. The fuel gauge now reads 1/2 full, which is about right. Maybe the C313 was just not plugged entirely in or the sending unit was stuck.

I also spoke to my brother in law. Before he gave up on getting this car to run, after he replaced the FP he WAS getting pressure at the TBI. His issue was the dead injectors and bad ECM. I've fixed those issues but now I can't get fuel pressure, oh the irony!

On a side note I thought about an easy way I might drain the fuel tank. I think the filter lines are below the tank. If I loosen them I might get a good gravity siphon going. I guess we'll see if and when that time comes.

Six_Shooter

iTrader: (2)

The purple wire at the tank is the gauge wire.
Black is ground.
Grey is fuel pump wire.

The purple wire should give you a range of voltages, depending on where the float is, or amount of fuel in the tank.

The grey wire should get 12V for about 3 to 5 seconds when the key is turned on, and then shut off, until the engine turns over, at which point it should see 12V again.

The 2 pin connector in the picture above is for the brake pedal. Should be for TCC lock up, if memory serves me on the brake switch wiring colours.

JVince

Excellent, thanks for the info. I'm hoping it's either the pump that has gone bad from just sitting for months, OR a short between C207/208 and the C313. Hopefully not both . I'm going to send 12v to the gray C313 with a ground to see if the pump turns on. If not I guess I'll have my answer. I'll also double check the gray for 12v on key turn and start attempts. I'm fairly certain I wasn't getting any voltage at any time from that gray wire though.

Now for a really stupid question: When I'm checking these connectors should I be doing it with them connected? I'll normally disconnect them and check the side coming from the power source. In example with the C313, the wire coming out of the body, not the lead from the tank. If I need to check them while they're connected I may have to strip the insulation a bit, I don't think my probes will reach all the way in to some of those terminals.

Thanks again guys, I feel like we're narrowing in on the problem!

* I just thought of another way I could check that gray wire at C313. If I put 12v to the G pin of the ALDL it should send 12v all the way to the pump correct? That way I can check that C313 wire without having someone crank the motor. I know I'm probably attacking the same issue from five different angles but I like to be certain before I start yanking out exhausts, buying pumps, ripping out interior, etc.

EagleMark

Your right some voltage readings need to be connected. But in this case you can disconect the gray wire and check for voltage with a multimeter grounded.

If you get no voltage at the tank on gray wire go back to the fuel pump relay and check there. Like Six Shooter said, will get 12ish volts (batterey voltage) when you turn key on for a few seconds then it turns of until you crank/run.

Not sure on your vehicle but my suburban has a red wire with conector on the fueel pump relay, hooked to nothing. It is to prime/test fuel pump if you add voltage to it from a jumper wire. HTH

JVince

I get 12v at the FP relay from the tan/wht and red wires. 12v applied at the FP relay or the G port of ALDL doesn't turn the pump on. At this point I'm pretty sure the pump is bad but I want to confirm voltage getting TO the pump . If I don't get 12v at the C313 gray wire (with either key crank or 12v applied) it must be a bad ground/connection at C207 or 208 I guess. I think those are the only other connection points in the fuel circuit.

EagleMark

I'm not sure of conection points but think your finding your problem. Gray wire going into fuel pump has to have 12 volts when key on (first few seconds) then on at crank or when engine is running of course.

Also could be a bad ground coming out of tank to wherever it grounds! My K5 was grounded to frame near the tank and was faulty once...

JVince

I checked the ground at C313 with my multimeter and it read zero resistance so they should be good. I thought the purple was the 12v when I tested so I was focusing on that one, there's a good chance I missed the 3-5 second window on the gray. That's why I'm planning on putting 12v to the ALDL terminal before I check the gray C313 again.

To be honest I'd MUCH rather drop the exhaust and tank then to hunt through wires looking for shorts. I'm mechanically biased .

EagleMark

Yeah but, you could drop the tank, install a new pump and VIOLA! still have to find a wiring problem...

JVince

Don't jinx me! If I can't get 12v at the C313 I'm probably going to dig around for the short first. The factory shop manual at $150 is looking cheaper every day

EagleMark

Sometimes it's easier to run a new wire than find a short. But don't leave a short. In this case you could disconnect the power at the relay so you don't have power going somewhere to a short. Then replace that wire from relay to tank.

JVince

I was considering that (if it turns out to be a short) but I thought some people here would see that as a hack fix :P. If I can get the pump to fire and it turns out to be lack of voltage at the tank... yea... that solution has its merits!

EagleMark

It's an accepted practice from a mechanics point of veiw. Could be considered a hack from the camaro community and definatly not a show car repair. But if done right no one would know but you...

JVince

If you check out my signature I'm probably already an outcast . This car is my wife's new toy, I'm just trying to get it running like a top so she can do whatever she wants with it. Definitely not a show or concourse project. I have to admit I have a soft spot for that year range. Reminds me of high school and drivers ed training. Same year, model.

EagleMark

Actually your signature is blank...

JVince

Strange. On all the other posts it showed up.

JVince

Ok I think we've pretty much nailed it. I double checked the tan/wht power coming from the FP relay, good 12v there with key on. With 12v applied to the G pin of the ALDL I get 12v at the gray C313 connection (body side). On a normal key turn I also get 12v at that wire for 3 seconds. 12v applied to the pump side gray wire (with the black pump side wire grounded) no pump noise or fuel pressure.

Looks like I'll be siphoning gas and dropping exhaust this weekend

Thanks to everyone, especially ASE Doc and EagleMark for all the information and putting up with my new car/GM newbie-ness.

I'll post a follow up once the new pump is in.

EagleMark

ASE Doc is the helpful one! I was just Chevy moral support!

Since the pump was recently replaced you may find a loose conection on the wire in the tank. Anyway glad your on the way to recovery...

ASE doc

I'll say I'm sorry that you have to go through this, but it's really not that bad. Just take your time. Be sure to buy a good pump. The two I recommend are AC Delco, or Bosch. Carter or Airtex, not so much. As EagleMark suggests, you may very well find a poor connection in the tank. The new pump has to be connected to the sending unit using butt connectors. Poorly installed butt connectors are very common.

I certainly recommend, since you have to drop the tank anyway, go ahead and replace the pump. Especially since you don't know what brand of pump was put in before. Be sure when you replace the pump that you perform solid crimps on the butt connectors. The tool you use here is important. I recommend Klein brand crimpers.

EagleMark

or if you can do it safely!!! I solder new ones on once it is removed. As ASE Doc said crimp is important, solder is better.

ASE doc

EagleMark, Have you had success soldering to the OE sending unit wiring? The wire used looks to be stainless steel. I don't know if it can be soldered. I've repaired old sending units where I had to resolder the lugs passing through the metal cover but I don't recommend this for any but the most experienced electronics techs. The insulators on these lugs are made of plastic and can easily be destroyed by the heat of a soldering gun.

EagleMark

Yes! But I have a good soldering station were you can dial in heat. I tend to use it higher than needed but then it's such a fast solder the heat does not have time to transfer to far past what you want to heat up and solder. My soldering station also recovers from heat loss very quickly.

Just for guys reading or trying don't forget when I said "if you can do it safely" I meant it has gasoline it it and fumes on it and it has to be drained and cleaned OBVIOUSLY so you don't blow up!

JVince

Thanks for the suggestions. We've already bought the pump. We managed to drop the exhaust, unbolt the traction bars and brackets and remove the heat shields before we ran out of time on Saturday. A baby shower prevented us from finishing up. Also siphoned out the gas and put in a new filter. It's raining today but I'm thinking maybe another 45mins to get the axle dropped down and tank out. Then I'll get to see the previous replacement pump work. While I was unbolting the exhaust from the cat I noticed the end of the speedo cable. No gear, just a chewed up and bound up bare wire

Also some copious amounts of oil on the bottom of the pan. We'll see how many drips, drops, noises and smoke puffs show up after we get her running.