Firefox64

Hello, guys and gals.

First time poster but long time lurker. I'd like to first off thank so many of you for helping me out with my issues over the last year that I have been in the shadows. I've learned a lot about my truck and I do want to start helping out others when I can. I've been a long time member of a Fiero forum and hope to help out here, too.

Ok....my issue. I have a '98 Suburban with a Vortec 5.7 that was completely rebuilt just over a year and roughly 10,000 miles ago. Truck has been reliable and running beautifully. Back in February I parked the truck for a couple of weeks just before a nice big snowstorm. I have a snowplow truck that I use when necessary and we had a crappy month for snow so the '98 sat. When I went back to bring it back out it wouldn't start. Crank fine and smooth but no fire. Started to go through stuff and found nothing. When the engine was installed I put in new E3 spark plugs, a set of Bosch spark plug wires and new cap and rotor.

First off, check fuel pressure. Key on, 62 PSI. Cranking 59-61. Fuel gauge is fluttering consistantly which tells me that the injectors are firing. Spark plugs are getting wet. No fuel issue. I do have the replacement Delphi injector set in place of the original CPFI setup so the fuel system on the engine is good. Newer fuel pump and regulator. Good fuel pressure....no issues there. Starting fluid did nothing ( just to eliminate that ).

Second, check spark. Pull coil wire and check for cranking spark. Spark is there. Seems ok. Check spark at the plug. Spark is there. Seems weak but strong enough to fire. Check wires. Wires all have proper resistance including coil wire. Spark plugs? Maybe the E3s aren't holding up. Replaced spark plugs with a nice set of AC/Delco Iridiums.

Now my screw up. I got this truck without an engine. The truck had been purchased for the engine and after the engine was removed I aquired the truck. Bought a motor, had it rebuilt and installed it. I do know that there was some minor damage on the front of the truck in the past and some parts had been replaced including the radiator shroud. When I installed the new plugs I glanced at the emission decal on the shroud and read .035 in. for the gap. Didn't think anything of it. New A/C plugs out of the box had a bigger gap so I regapped them to .035. Installed them and the truck fired right up. No issues, no codes. Shut it off and buttoned everthing up. Didn't drive it at that point.

For the next hour or so something was bugging me about those plugs. I finally looked into it and realized that the .03 gap was wrong and a .060 was the proper gap. Pulled the plugs, regapped them and reinstalled them. No fire. Nothing. No pop. Crank fine. Pulled a plug. Spark. Internet search. More internet search. Found TSB about bad crank sensor throwing off timing by 50 degrees. Fits my problem. Pulled known good crank sensor from another motor and no change. Check ignition control module. Replace cam sensor with known good sensor. Run seperate 12 volt line to input on coil to bypass ignition switch. Check wiring. I'm ready to start it on fire.

I have several knowledgeable guys pulling thier hair out. I'm somewhat knowledgeable myself and have been tinkering with this thing for quite a while with no luck. The weather hasn't been the greatest so I'm not going after it every evening.

Anyone have any thoughts? I appreciate any input.

Thank you for taking the time to read all of this.....

Mark

kevinkpk

You stated earlier in your post, ignition was weak, two things, 1) fuel, what condition is it. I know you have 62 psig, but what about condition. 2) what color is the arc? I'd suggest even if it is cranking to jumper it while trying to start. That would elminate weak battery.

Firefox64

Fuel condition should be good. Just over 1/2 tank and was filled about 2 weeks prior to parking it. This is ( was ) a daily driver truck and had no starting issues before this. The color of the arc was a weak blue to orange. It seemed to be stronger than weak orange spark but not quite a strong blue spark.

In regards to jumping while cranking, we did attempt that with a dual battery truck and had 14.74 volts at the battery terminals while cranking. The battery was installed new when the engine was installed and it's holding power well. At that time we had a 12 ga. jumper wire directly to the coil input just to eliminate the entire wiring harness between the battery and coil as a culprit. No change. Coil is new and tested to verify it's good. After reading the TSB about the crank sensor that seems to fit the symptoms but a good sensor didn't change anything. This does seem to be a timing issue. Installing the plugs with the wrong gap eliminates the mechanical issues but that larger gap seems to be throwing something off.....like the added electrical demand is changing something. I do have a set of factory service manuals and I've been scouring over the schematics to find out what is connected to where and how the system is set up. I haven't had anything jump out at me. The service manyal troubleshooting test procedures pointed to the ICM.....but a good known unit installed did nothing. We checked all the wiring and haven't found anything yet. My ICM works in another vehicle just fine.

Thanks for taking the time to help.

Mark

Joe In NY

BE CAREFUL when gapping Iridium plugs! if done wrong you will RUIN the plug, iridiums are preset and have to be gapped specially... this might be your prob but idk.

73shark

Jumper cables only recharge a dead battery, not supply starting current. The connection is just not good enuf to conduct several hundred amps of current. That's why it's recommended to let the good battery charge the dead one for a few minutes before trying to start the dead unit.

Firefox64

The iridiums were gapped with the proper tools. The jumpers were used to just make sure there wasn't any issue with available voltage. The battery was charged several times just to keep it topped off between attempts to start.

I appreciate all the advice. I figure that this issue is something far fetched and possibly something stupid that I'm overlooking. I've had several fresh set of eyes looking at this and nothing so far.

Thanks, guys.....

Firefox64

Rechecked fuel pressure and swapped in another known good crank sensor. Nothing. Started going over the wiring again and still no sign of anything amiss. Grounds are good......

Morland1

Here is something you can try. My 99 Tahoe would not start a couple months back, but looked like it had good spark at the plugs. If you have an old distributor cap and rotor laying around try changing them out and see what happens, I am guessing it might be the rotor, maybe something making it fire out of time. I did not pin point it down to which it was on my 99, but changed both out with an older set I had in the garage and it started right up. Or maybe you have a friend that has a Chevy you can swap them out with. I would hate to tell you to buy a new set for $70 or higher, and it not fix the starting issue.

Firefox64

When the engine was rebuilt I bought a new cap and rotor set along with a set of wires and plugs ( the E3s ). One of the first things I did was replace the cap and rotor ( under warranty ) as it seemed that I had a decent spark at the coil but not the plug. That didn't change anything.

I'm going to pull the wires as soon as the rain lets up and recheck the resistance of the plug wires.....just to make sure.

Thanks for taking the time to help.

Mark

Joe In NY

I would do as Morland1 said. Weird things happen for no reason. such as last summer.

Ford 351W: Our friends last spring gave their boat the regular tune up. New plugs, cap, and rotor. (coil and plug wires were still relatively new). Ran great! Later that summer they accidentally ran out of gas and got towed to gas pump and got gas. When they started it, it ran like crap! Had a really bad knock and ran horrible. So we went over and investigated. Spark was good but when we unplugged Cyl. 7 run MUCH better... Swapped the the dist. cap with old one, good as new. turns out the new cap had a hair-line crack where cyl #7 was hooked up, so it was arcing to cyl #7. But running out of gas caused this... How? No idea....

Just cause its new doesn't mean its fine...