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6.5 Chevy Cheyenne 3500 Stalling and No-start

Rockabillyrat said:
There is no sensor in the GP relay to the PCM. Only the control wire that the PCM grounds to control the relay.

Does ECT read correctly on the scanner
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Yes. I checked it against my inferred temp gun I did just go out there and bypassed the delay relay putting it back to normal operation. Haven’t started the truck all day. Key on and I got to count 6 seconds and she fired right up! Thought I do have a PCM installed that I got from the junkyard from a 94 model. The truck is a 95.
I had snagged the pcm a few weeks ago when I stumbled across it for $12 I couldn’t resist lol.
 
Only reason I have the extra pcm is because I wanted to play with doing my own tune but didn’t want to mess with the original one. I just haven’t ordered the chip programmer yet
 
One of my goals in the tune was to add 2 seconds more glow time to the table. Along with maybe a little more fuel per engine load but I’m still reading and learning about that stuff
 
Sounds like you may have found your problem! I'm seeing more and more PCM issues on 90s trucks. I've gotten in the habit of opening them up if I have a weird problem I can't narrow down. Especially the Fords, the capacitors leak over time and cause alot of weird issues.
 
The amperage test is effective just like the ohms test. So long as the glow plugs do not have any crystallization on them nor have they been burning away, either test will work.
If voltage is the same, ohms and amps react opposite each other. Picture a teeter-totter where volts is the fulcrum and the kids on opposite sides are ohms vs amps.

The problem is this:

Some additives in fuels (yes gonna blame ethanol/methanol yet again) cause the same crystals to form on the element surface that happens with starting fluid. That part of the fuel is simply too flammable and rather than burning evenly, it is attracted to the hottest part of the combustion chamber much like your finger print oils damage a halogen bulb.
Grey hairs like me remember glow plugs lasting really long and now the don’t because of the fuel. Meh, they are cheap enough to not cry over 20% less life.

Anyways- when the element of the glow plug burns up, it gets shorter. this happens at faster rate with advanced timing. It happens naturally even if timing is perfect. As the glow plug gets shorter there is less material there, so the electrical resistance goes up it is a smaller heater. The amount of power (amps) it draws goes down because it is a smaller heater. So this is how ohm or amp test can tell you it is bad. And this is how the instructions were set years ago to test.
So Why is this not the go-to method anymore?

Glow plug engines were never approved for starting fluid. Most folks know it can instantly destroy if there is a hair too much used, or non turbo diesels with glows would cause a flash back through the air filter and injury ensued. But the lessor known issue is the ether would burn on the glowplug and cause the crystallization of the element itself. This adds an insulating crystal that is still somewhat conductive so now the ohms lowers. And the crystals absorb way more electrical energy than the element does, so amperage rises at same time.

So, you can have a glow plug that has burned away enough of the length but has crystals built up - so it will have “proper ohms and proper amperage draw”. But really the element is now to small to heat the area, and has a heat insulating layer on it. So good test by meter but bad performance.

And I have found the opposite also. The glow plug was working well- got nice and hot. But the crystals formed close to one end and throws the resistance way off. But the far end of the element is just cooking away. Amperage draw was still the same because the crystals although dont put out good heat- absorb a lot of electricity. The crystals are just a very inefficient heating material.

The crystals btw are about the size of table salt cubes but no sharp edges. So don’t expect to see some huge growth on it. It really just is not as smooth as original.

This is why I quit doing the tests. I chased other issues having ohmed them as ok. Then to double check them and verify proper circuitry of fuseable link/ relay/ ignition/ etc I did clamp meter afterwards.

2 guys in fleet shop looked at it when I was getting frustrated, and I went for lunch. Came back and a guy just threw a set of plugs in because he didn’t know any other tests and just said “sounds like glow plugs”. Worked perfect, so I went to testing and inspecting. Almost smashed my fluke 87 and my ammeter. A different guy that was off that day came back and said he found same thing and couldn’t understand why. So we started checking it out and getting the engineers involved. One of the big clues to them was when we realized it was the 60% ethonal with #3 diesel fuel test trucks. We couldn’t get 25,000 miles out of a set. Haha.

Our move in the shop became swap in a set and send the truck on the way. Then bench test and the good used ones went in the ‘ok’ parts bin. Works good for fleet and diy yourself- but obviously not for paying customers.
 
Rockabillyrat said:
Husker's comment on GP isn't 100% correct. High voltage for too long will fry them. BUT, under very cold starts GP will post cycle after the engine is running. The short cycle at 14v doesn't hurt them.
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Again, we were talking about when trying to START his vehicle, since early on in his post thread he had talked about battery issues and no matter how long he cranked, it wouldn't start. It was a warning NOT to try a glow plug cycle and start off a charger. Throwing out superfluous information on your part, like post-start short glow cycling in cold weather, is meaningless to the issue at hand. You being a smartass little punk is not helping him, either. I've been wrenching on 6.2/6.5's since the first CUCV's came into inventory in the military, probably before you were born. If his vehicle was running, he wouldn't be here in the first place seeking help, now would he?

If you're trying to win the award for F*cking *sshole of the Year, you're well on your way. Oh, and BTW, my SnapOn cabinet and chest set was free to me. And my 55 year old SnapOn ½" drive torque wrench I was using clear back in the 1960's still holds calibration every time it's been checked and serviced by the local SnapOn dealer.
 
dbrannon79 said:
Only reason I have the extra pcm is because I wanted to play with doing my own tune but didn’t want to mess with the original one. I just haven’t ordered the chip programmer yet
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And the fun thing about the 94 & 95 OBD-I's is that the PROM chip is physically removable from the ECM! So if there's something electronically whacked with the ECM box itself, you can swap the PROM into a good box and keep on rolling. The PROMs were programmed vehicle-specific, like a 94 'S' V.I.N. C1500 5 speed manual wouldn't use the same PROM chip as a 94 'F' V.I.N. C2500HD C&C automatic. Of course, all you have to do is remove the small cover on the back and read the PROM code on the chip.

Somewhere back about 13-15 years ago there were a couple of threads on here where members posted files for programming fueling rates, shift schedules, etc for them and a member even built an adapter to switch between PROM chips on the fly to change tunes from economy to full-on race and four others in between. Those posts are so old, I don't know if they, let alone those files, can be pulled up with all the forum software changes/updates made since then. If you can, it could save you some time, give you some hints and make what could be frustration into enjoyment. Me, personally, I'm not into the electronic monkeying with programming end of things, I prefer wrenching for results and then buying a tuned PROM/ECM to fit those modifications for the results I want.
 
Rockabillyrat said:
Husker's comment on GP isn't 100% correct. High voltage for too long will fry them. BUT, under very cold starts GP will post cycle after the engine is running. The short cycle at 14v doesn't hurt them.
Click to expand...
I saw on Rock Auto today that a reason for failure is from running direct 12v power to "a 6v plug" makes me question why so many different volt suggestions. Just look under the AC delco plugs and see the more info tab. That said. I need plugs. My cycle time is not even a second. Ive never replaced them in 5 or 6 yrs and the privious owner isnt around to ask so im gonna assume they are bad and eliminate them as a cause to my root issue($)
 
dbrannon79 said:
It's hard to test them while in the block. start with the 4 glows on the drivers side of the engine. they should use a 10mm socket to unscrew them depending on what style are installed. pull the spade connectors off all 4 of them and pull them out of the block. if they are swelled up the tips will not pull out from the block and will require a tool to pull them. be careful not to break them off in the head. if you do break one off. it can be accessed by pulling the injector for that cylinder and using a magnetic stick in the hole.

this is why I suggest starting with the side opposite of the turbo first. the passenger side is a PIA if one breaks off.

mark them as you take them out so you know which cylinder they came from. visually inspect each one (post some pics here) if they all look good, then get you a set of jumper cables and test each one by applying 12v to them for 5 seconds. each should glow red hot on the tips within that 5 seconds.

once you have verified that the glow plugs are good, apply some anti-seize on the threads and re-install, reconnect the wires. if the glow plugs look bad or do not get red hot. do not go to the next step until you have a set of new glow plugs in hand.

Next step: checking for power to the glow plugs..
get you a test light and a screw driver... connect the test light clamp to a known good ground (brake line or neg bat terminal) check test light to verify it lights up on the pos bat terminal.

touch the end of the test light on one glow plug terminal and use the screw driver to cross the two large posts on the glow plug relay. do not hold the screw driver on there for more than a second or two just long enough to see the test light light up. do this for all 4 glow connectors on that side of the block. you should have the test light light up each time you cross the glow plug relay terminals.

once you have the results, report back with your findings. and we will instruct you on your next steps.
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Ok ill do this. Im gonna buy new plugs just to have fresh ones. Any good old ones will become my spares. Im having a time finding the g plugs on Rock Auto and eBay wants to much. Are the AC Delco factory ones the same as the G models?
 
dbrannon79 said:
though i have the 60g's installed on my rig, my truck has a short cycle problem that I have not been able to figure out. even unplugging the ect sensor they will only cycle on for 5 seconds which gives me a hard to start issue. I ended up temporarily installing an adjustable time delay relay on the trigger wire (yellow) from the GP relay. set it at 8 seconds, hard start problem is gone, but it also sometimes re-triggers the relay for another 8 seconds after the engine starts up. that hasn't given me any trouble yet.

I know eventually I need to figure out what is causing me to only get 5 seconds out of the normal time. I have a hunch it's something in the PCM. unless there is some sensory in the glow plug relay it's self that feeds back to the PCM.
Click to expand...
I hear your frustration. Id kill for even five seconds at this point. I get less than a second. Light on..light off.. (click click)
 
dbrannon79 said:
It's hard to test them while in the block. start with the 4 glows on the drivers side of the engine. they should use a 10mm socket to unscrew them depending on what style are installed. pull the spade connectors off all 4 of them and pull them out of the block. if they are swelled up the tips will not pull out from the block and will require a tool to pull them. be careful not to break them off in the head. if you do break one off. it can be accessed by pulling the injector for that cylinder and using a magnetic stick in the hole.

this is why I suggest starting with the side opposite of the turbo first. the passenger side is a PIA if one breaks off.

mark them as you take them out so you know which cylinder they came from. visually inspect each one (post some pics here) if they all look good, then get you a set of jumper cables and test each one by applying 12v to them for 5 seconds. each should glow red hot on the tips within that 5 seconds.

once you have verified that the glow plugs are good, apply some anti-seize on the threads and re-install, reconnect the wires. if the glow plugs look bad or do not get red hot. do not go to the next step until you have a set of new glow plugs in hand.

Next step: checking for power to the glow plugs..
get you a test light and a screw driver... connect the test light clamp to a known good ground (brake line or neg bat terminal) check test light to verify it lights up on the pos bat terminal.

touch the end of the test light on one glow plug terminal and use the screw driver to cross the two large posts on the glow plug relay. do not hold the screw driver on there for more than a second or two just long enough to see the test light light up. do this for all 4 glow connectors on that side of the block. you should have the test light light up each time you cross the glow plug relay terminals.

once you have the results, report back with your findings. and we will instruct you on your next steps.
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Love your answers man. Your very articulate and i can picture what you are saying so ot helps thanks. Im gonna start soaking them tomorrow. Ill do the removal and take off my battery box and air intake so i can try to bist off the passenger ones. Im installing all new ones seeing that's how I've never replaced them in 6 years, I don't know when the previous owner did so I'm assuming they're probably in need of an exchange. Also, I've had hard starts and battery issues for a couple of years and I've been putting these things through hell I assume. I even started manually jumping the terminals on the relay about a year ago especially during the winter time so that I could get back and forth and I'm sure I probably left the screwdriver on there a little too long at points so who knows what I've done damage wise to these poor little glow plugs. I think a fresh set would eliminate that is an issue for me and I assume it would probably clear up at least one of my gremlins. I live in a pretty warm climate and my truck has no rust at all. I'm hoping that these things come out fairly easily because I don't have any WD-40 right now and my truck is my only transportation. I did get a back tire on my Harley so if it doesn't rain this weekend I can get down to the store and grab some wd-40, anti-seize, and check the prices at AutoZone although I know that O'Reilly's in AutoZone have one hell of a market on this stuff. That's why I call O'Reilly's O'Reilly's Auto store "OH, REALLY?" BECAUSE THAT'S WHAT I SAY EVERY TIME I SEE THEIR PRICES
 
OH SHOOT! forgot to mention- there is a LOT of knock off (fake parts) out there now.
Go to a local brick and mortar store that is AUTHORIZED AC Delco.

I like rock auto, but i had bosch plugs from there destroy my piston and rock auto told me pound sand, along with bosch because rock auto was not an authorized dealer. The bosch used to be the other recommended one but obviously not anymore after me and many others started having issues.

AC Delco 60G. Oriellys has them- since you said you are going there anyways.

I don’t normally like just buying parts before testing, but in your scenario- I think your fine.
 
Rockabillyrat said:
Ok I reread this thread and here is my 2 cents. (I missed you posted codes)

For the battery draw you need to do an amp draw test. disconnect the negative battery terminal and hook your amp meter up in series. One lead on the battery and one lead on the negative cable end. You must disconnect the second battery too or it will throw off your readings. Let it sit for 30 min and check the amperage draw. Anything over .050 amps is too much. If its too high then you can start pulling fuses one at a time and look for the draw to go away. (You can also voltage drop a fuse and see if its pulling amperage by putting your meter in millivolts) If you pull all the fuses and there is still a draw then disconnect the alternator and starter.

For the shot cycling GP I would look into your ECT sensor since it set a code. You can ohm the sensor and compare it to a temp/ohm chart for the sensor to see if its reading correctly. But that wont tell you if there is a bad wire or if the PCM is seeing the right temp reading. Unfortunately you need a scanner to see data. Also the 57 code you reported my be part of the issue. That means the 5v ref is shorted. It could be a shorted sensor or wires. Check for 5v on the ref wire (Easy place to check is at the MAP sensor). If you have 5v wiggle the wring and see if it drops out. If its at 0v, unplug each 5v sensor one at a time and see if the 5v comes back. A shorted sensor can pull the whole circuit down. If thats gets you no where then I highly recommend finding someone with a Tech2 to come out and scan it and look at data.

hope this helps
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Okay this is getting to be close to the top of my pay grade but I'm going to give this a shot as well. I bought a new meter the other day because both of my crapped out so I just went ahead and got a brand new meter yesterday because yesterday because my other two crapped out, and I hit the third one with a sledgehammer because it was one of those freebies from Harbor Freight. I can say this... When I would unplug the sensor that's on top of the engine intake plenum, it basically has a red grommet on it and it plugs right into the top of the motor and has what I think is a 3-pin plug.. for some reason for the last year or so before all this S#&# started, I noticed that I noticed that when I unplugged it sometimes it would start right up. Other times when I plugged it back in it would start right up. So I would go back and forth from the driver's seat to the plug on a daily basis I was assuming that it went bad so I just replaced it with a new one so it is brand new but the old one might not be bad like you said it might be the wiring. From the position of this sensor, I'm assuming that it probably regulates gas and air flow? That is no Bueno if it was bad so....got a new one on. I noticed there's another one that looks very similar looking sensor on the driver side firewall almost right where the windshield wipers are. Thing is, there is a air hole or a breather hole on this sensor and there's no tube hooked up to it. I have never seen one hooked up to it but when I took it off to inspect it one day I noticed there was no air tube on it I wonder if I have a tube missing from this sensor
 
here's a pic of a possible sensor your describing. Searched but couldn't find a thread that identifies underhood components, maybe someone else can find it.
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