Tug RubNuts
Member
- Joined
- Apr 9, 2021
- Member Number
- 3755
- Messages
- 7
Hey all, I've been a long time lurker on the old site and now on this site for a little while now but this will be my first post, so bear with me. I want to start this off by saying I'm NOT a mechanic and I'm not super experienced, I'm just someone trying to learn to fix busted old trucks the hard way. I don't have access to a shop and don't have nearby mechanically inclined friends or family. Everything I do I have to do on the garage floor or the auto store parking lot, with instructions from a Haynes manual or a YouTube video if I'm lucky. With that being said, I'm here looking for some input from those who might have a little (maybe a lot) more experience with diagnosing vehicle symptoms. I tend to type a lot and want to provide as much relevant info as possible so I'll try to highlight the important bits, but here goes nothing.
Some Background: Last summer I bought a 1998 Chevrolet K3500 because I have an addiction to big old trucks and I haven't learned my lesson yet :rolleyes: (and have dreams of using it to tow a future RV). It's a 4 door, 4 wheel drive, long bed DRW truck with the Vortec 7400. Fuel pump seems to have been replaced because of the "access hole" cut in the bed, and according to the PO the brake lines are new (they look pretty good) and the transmission is a newer unit as well. Odometer is frozen at just under 100k. Was supposedly used by an older couple to tow their RV almost exclusively in the summer. The truck is clean enough to back that up and also has 12,000 pound GVWR plates on it, which means someone went through the trouble at the DMV to get it changed as the sticker in the door says 10,000 pounds GVWR. But, the PO was shady as hell so it could have been used for anything for all I know. When I first bought the truck it was almost undriveable because it would completely die while going down the road. Sometimes it would cut out for a few seconds and kick back on after I coasted over to the shoulder and other times it would just start bucking and cut in and out several times in a second. I Eventually managed to white knuckle it home, and upon further inspection under the hood there was a random ass orange wire sticking out by the relay panel that seemed to lead under the firewall. I grabbed the wire strippers and crimped a ring connector onto the wire and then placed it around "Auxiliary Post A" on the fuse relay center and put a nut on top of it, next to a red wire that was mated to "Auxiliary Post B" in the same way. The next time I drove the truck it cut out and back in once, then stopped doing it completely. Later, on a road trip out of state, the truck started acting up again and after I pulled over and popped the hood I saw that the nut holding the random ass orange wire had come loose, so I tightened it and was back on my way. After that little bit of jury rigging the truck always ran like a top, but started hard when it was warmed up and I swore on a few occasions I could smell gasoline when cranking the truck after it had reached operating temperature (in situations like shutting the truck off at the gas station and starting it up right away afterwards). I honestly am not sure this has anything to do with my current issue but want to provide as much information as possible.
The Issue(s): The gauges work except for the oil pressure gauge which turns on and off as the truck bounces along and fuel gauge which comes on once in a blue moon. If I put just the right amount of pressure in just the right area on the about-to-fall-off dash trim those two gauges come to life. I'm pretty sure that has nothing to do with what's going on but hey, you never know. Also, one of the exhaust manifolds is cracked. After taking the truck on a trip to Colorado and back there was an incident where the truck died on me in a parking lot. The fuel gauge looked low so I bumped the key, the truck fired right up, and I drove it over to the gas station I was next to. However, after filling up the truck it refused to start. I had a dinky little inline spark tester in the glovebox so I put that on cylinder 1 (or whatever the front driver side cylinder is) and it looked like it wasn't getting any spark. I unplugged the spark tester and plugged it back in multiple times. After waiting a few minutes and trying the key again it sounded like a couple cylinders would hit and it felt like the truck was about to jump to life, then that sound and feeling would go away and the truck would just crank and crank with nothing happening. Got a rollback to haul the truck to a local shop and they called me the next afternoon saying the truck started right up and ran flawlessly! After that I didn't have any more issues until about a week or two ago when the truck died on me again after going over a railroad crossing. I pulled onto a side street and popped the hood and once again busted out the dinky little inline spark tester
. I had my buddy in the truck hit the key, and it looked like it wasn't getting spark again. I wanted to make sure I had a snug connection between the spark tester and the wire so my buddy took the key out of the ignition, I unplugged the spark tester and plugged it back in, and had my buddy hit the key again. The damn thing fired right up like nothing ever happened. On both of these occasions I checked the random ass orange wire and it was snug. I don't know what changed recently, but now the truck starts if you even think about bumping the key regardless if it's below zero or the engine is all warmed up, which is nice. However, the biggest issue now is the truck runs like total shit until it reaches operating temperature. I haven't verified this yet, but it sounds and feels like it's only running on 6 or 7 cylinders at idle when it's cold. When I hit the throttle it sounds like the other 1 or 2 cylinders are cutting in at higher RPMs, and then as the truck warms up to operating temp it gradually smooths out and everything sounds like it's running right.
Everything I have done to the truck since buying it: Jury rigging mentioned in the background section, replaced the PCV valve, oil and oil filter change, air filter, new driver side window motor, replaced the front differential (found out the hard way that the leak under the truck wasn't just power steering fluid), new hydraulic brake booster, new plugs and wires. The truck had to go to the shop to get the replacement front differential I put in resealed (my fault for not thinking ahead), and had to go back again because the "remanufactured" hydro boost I was sent went in perfectly except for the hole that one of the high pressure lines threaded into was out of spec. I found that out the hard way when I fought with the line to get it threaded in and tightened as far as it would go. I triumphantly started the truck and all was good for about 5 seconds before power steering fluid started spraying out from around the nut on the end of the flared line, coating several wires and connections against the firewall in the driver side corner
. I immediately thought something would be screwed up, but didn't notice anything different about the truck after it happened. That was a few months ago, so I'm not sure if it could be related to what's going on now. I tried three different replacement lines with no luck 
. Luckily the shop was able to get one threaded in there, so I avoided having to take the whole unit back out and sending it for replacement. The shop also replaced the sensor for the temperature gauge on the dash.
My (un)educated guesses: I'm gonna start this section off by saying that there are no warning lights on the dash, so the truck isn't exactly giving up any clues. I initially thought the random ass orange wire was for the fuel pump and the truck was dying because the fuel pump was constantly cutting out, but if both those guesses are true I don't think that explains why the truck didn't seem to be getting spark on the occasions I tested it. So, I don't know if I'm wrong about both of those things or if the random ass orange wire has nothing to do with what's currently going on. My next uneducated guess is that some godforsaken length of exposed wiring is grounding out where it shouldn't be as the truck bounces down the road, but that doesn't necessarily explain why the truck runs so rough when it's cold. Uneducated guess #3 is that the cap, rotor, ignition coil, or all three need to be replaced and are just making the truck run funky. My final uneducated guess is that the ECM is going bad, is already bad, OR is causing the truck to run weird because of the cracked exhaust manifold (messing with the O2 sensor or something?). Maybe the timing is off and I don't know the symptoms well enough to recognize it.
I'd like to hear your educated (or uneducated) guesses and theories, and tell me why you think mine are wrong or right. Pirate/Irate has some of the best tech on the web so I'm sure there's a lot of people here that know more than I do, and I'd be grateful for any ideas or help you have. Thanks for reading my big ass post
.
Some Background: Last summer I bought a 1998 Chevrolet K3500 because I have an addiction to big old trucks and I haven't learned my lesson yet :rolleyes: (and have dreams of using it to tow a future RV). It's a 4 door, 4 wheel drive, long bed DRW truck with the Vortec 7400. Fuel pump seems to have been replaced because of the "access hole" cut in the bed, and according to the PO the brake lines are new (they look pretty good) and the transmission is a newer unit as well. Odometer is frozen at just under 100k. Was supposedly used by an older couple to tow their RV almost exclusively in the summer. The truck is clean enough to back that up and also has 12,000 pound GVWR plates on it, which means someone went through the trouble at the DMV to get it changed as the sticker in the door says 10,000 pounds GVWR. But, the PO was shady as hell so it could have been used for anything for all I know. When I first bought the truck it was almost undriveable because it would completely die while going down the road. Sometimes it would cut out for a few seconds and kick back on after I coasted over to the shoulder and other times it would just start bucking and cut in and out several times in a second. I Eventually managed to white knuckle it home, and upon further inspection under the hood there was a random ass orange wire sticking out by the relay panel that seemed to lead under the firewall. I grabbed the wire strippers and crimped a ring connector onto the wire and then placed it around "Auxiliary Post A" on the fuse relay center and put a nut on top of it, next to a red wire that was mated to "Auxiliary Post B" in the same way. The next time I drove the truck it cut out and back in once, then stopped doing it completely. Later, on a road trip out of state, the truck started acting up again and after I pulled over and popped the hood I saw that the nut holding the random ass orange wire had come loose, so I tightened it and was back on my way. After that little bit of jury rigging the truck always ran like a top, but started hard when it was warmed up and I swore on a few occasions I could smell gasoline when cranking the truck after it had reached operating temperature (in situations like shutting the truck off at the gas station and starting it up right away afterwards). I honestly am not sure this has anything to do with my current issue but want to provide as much information as possible.
The Issue(s): The gauges work except for the oil pressure gauge which turns on and off as the truck bounces along and fuel gauge which comes on once in a blue moon. If I put just the right amount of pressure in just the right area on the about-to-fall-off dash trim those two gauges come to life. I'm pretty sure that has nothing to do with what's going on but hey, you never know. Also, one of the exhaust manifolds is cracked. After taking the truck on a trip to Colorado and back there was an incident where the truck died on me in a parking lot. The fuel gauge looked low so I bumped the key, the truck fired right up, and I drove it over to the gas station I was next to. However, after filling up the truck it refused to start. I had a dinky little inline spark tester in the glovebox so I put that on cylinder 1 (or whatever the front driver side cylinder is) and it looked like it wasn't getting any spark. I unplugged the spark tester and plugged it back in multiple times. After waiting a few minutes and trying the key again it sounded like a couple cylinders would hit and it felt like the truck was about to jump to life, then that sound and feeling would go away and the truck would just crank and crank with nothing happening. Got a rollback to haul the truck to a local shop and they called me the next afternoon saying the truck started right up and ran flawlessly! After that I didn't have any more issues until about a week or two ago when the truck died on me again after going over a railroad crossing. I pulled onto a side street and popped the hood and once again busted out the dinky little inline spark tester
. I had my buddy in the truck hit the key, and it looked like it wasn't getting spark again. I wanted to make sure I had a snug connection between the spark tester and the wire so my buddy took the key out of the ignition, I unplugged the spark tester and plugged it back in, and had my buddy hit the key again. The damn thing fired right up like nothing ever happened. On both of these occasions I checked the random ass orange wire and it was snug. I don't know what changed recently, but now the truck starts if you even think about bumping the key regardless if it's below zero or the engine is all warmed up, which is nice. However, the biggest issue now is the truck runs like total shit until it reaches operating temperature. I haven't verified this yet, but it sounds and feels like it's only running on 6 or 7 cylinders at idle when it's cold. When I hit the throttle it sounds like the other 1 or 2 cylinders are cutting in at higher RPMs, and then as the truck warms up to operating temp it gradually smooths out and everything sounds like it's running right.Everything I have done to the truck since buying it: Jury rigging mentioned in the background section, replaced the PCV valve, oil and oil filter change, air filter, new driver side window motor, replaced the front differential (found out the hard way that the leak under the truck wasn't just power steering fluid), new hydraulic brake booster, new plugs and wires. The truck had to go to the shop to get the replacement front differential I put in resealed (my fault for not thinking ahead), and had to go back again because the "remanufactured" hydro boost I was sent went in perfectly except for the hole that one of the high pressure lines threaded into was out of spec. I found that out the hard way when I fought with the line to get it threaded in and tightened as far as it would go. I triumphantly started the truck and all was good for about 5 seconds before power steering fluid started spraying out from around the nut on the end of the flared line, coating several wires and connections against the firewall in the driver side corner
. I immediately thought something would be screwed up, but didn't notice anything different about the truck after it happened. That was a few months ago, so I'm not sure if it could be related to what's going on now. I tried three different replacement lines with no luck . Luckily the shop was able to get one threaded in there, so I avoided having to take the whole unit back out and sending it for replacement. The shop also replaced the sensor for the temperature gauge on the dash.My (un)educated guesses: I'm gonna start this section off by saying that there are no warning lights on the dash, so the truck isn't exactly giving up any clues. I initially thought the random ass orange wire was for the fuel pump and the truck was dying because the fuel pump was constantly cutting out, but if both those guesses are true I don't think that explains why the truck didn't seem to be getting spark on the occasions I tested it. So, I don't know if I'm wrong about both of those things or if the random ass orange wire has nothing to do with what's currently going on. My next uneducated guess is that some godforsaken length of exposed wiring is grounding out where it shouldn't be as the truck bounces down the road, but that doesn't necessarily explain why the truck runs so rough when it's cold. Uneducated guess #3 is that the cap, rotor, ignition coil, or all three need to be replaced and are just making the truck run funky. My final uneducated guess is that the ECM is going bad, is already bad, OR is causing the truck to run weird because of the cracked exhaust manifold (messing with the O2 sensor or something?). Maybe the timing is off and I don't know the symptoms well enough to recognize it.
I'd like to hear your educated (or uneducated) guesses and theories, and tell me why you think mine are wrong or right. Pirate/Irate has some of the best tech on the web so I'm sure there's a lot of people here that know more than I do, and I'd be grateful for any ideas or help you have. Thanks for reading my big ass post
.
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