91 suburban still Dead in the water no pulse at injectors

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Frank Compagnon

Supporting Member
Supporting Member
Joined
Mar 24, 2017
Messages
81
Reaction score
78
Location
Prince George,B.C. Canada
I have 3 GMT400s ,all running, and a few for parts. There's always things braking, because of age. Some Are- Distributor and disturber inner parts failure, no spark.
MAF sensor, never had much trouble with them, but sometimes...
IAC valve and IAC connector, too much air or none, Injectors ,have had some TBIs with bad gaskets and plugged injectors, injectors not firing or spray patter all-over-the-place, I have had good results using a hydro sonic cleaner

And thee best one is that electrical ignition switch down on the steering column, sometime it will still power up everything when key is off and out off ignition. Some times it will start and not start because the inside of the switch is worn out ,can cause some grief, intermitting voltage to areas it shouldn't and vise versa I just got 3 in from Rock Auto.
The one on my dually wouldn't shut off, even when I disconnected the battery, had to cut the power wire to the alternator to shut it down.
I would go at it, like I'm steeling it, hot wire , then reverse engineer (troubleshoot) it.
 

Eveready

I'm Awesome
Joined
Nov 29, 2017
Messages
1,342
Reaction score
1,634
Location
North Carolina
While I feel your frustration, the more I see of this thread the more I suspect a defective or failing fuel pump. Many members here have had brand new ones fail. The fact that it runs when you pour gas in it tells you something for sure. Also someone mentioned the possibility of a security system shutting off fuel. Have you adequately tested for that? Everyone here wants you to get this beast going and when you do it is going to be something simple and likely a face palm moment. Good luck!
 

Ed Hardy

Newbie
Joined
Dec 23, 2020
Messages
47
Reaction score
21
Location
atlanta
Well I won’t guarantee it’s not the fuel pump after all I did buy through Amazon but there again I can’t disprove anything else either. The gentleman before you with the ignition issues has a valid point also but I can't just disprove him either. I of put two of everything on this truck and the only thing that has worked so far is grounding out the injectors straight from the battery that worked, for a minute. I have ripped apart that steering column now twice the first time was for an all of a sudden violently loose knuckle joint and the second to replace the multi function switch which arrived days after I had put it back together I tried waiting on it but, US Postal Service why can you say. I didn’t find anything wrong the first go round except for the knuckle joint need to be tightened up but while I was there and it was gutted eent ahead and replaced the neutral safety switch and the ignition switch. She was operational when I did this and remain so until the day of the of the gauge installation. I figured you couldnt hurt while I was there I might as well do it she is a 91 after all. Even though she only has 72,000 original miles which is exaggerating because it’s really only 71,000 and change. The second go round I noticed as I precariously painstakingly took apart the steering column looking for something that I had done wrong or something gone awry, the only thing that I found in all that **** that GM puts in a Tiltsteering column was I had pinched One wire and that one wire is the brown wire. And like every time I turned a corner and thought I found something that would be it the brown had to be it! like we all know The brown wire spreads through a GM like a virus so I thought I had it. but nope, no avail. I re-replaced the key switch And at the-same time re-replaced the ignition switch also which I figured while I was in there “ do it again.”As if I needed more practice. Well that didn’t fix it either. Imagine my surprise. I traced wires through the fire wall down to the store out to the distributive all over that motor. I have a full truck wiring schematic and I follow them
Wire by wire until I found where the splices were and where all the grommets. sure, i know i created more damage just by tracing. I’ve gone back and fixed that also. So that’s the thing about being **** yeah too meticulous about doing things and then once you get it done you don’t trust your own work and you have to go back and tear apart and inspect it just to see . Well you can only imagine what my dash looks like after ripping it apart seven times.every time I thought I had it buttoned up , somebody would say something which would make me mis-trust what I had done and seen with my own eyes and I would take it back apart again . This is why the dash is not completely assembled this time because I will not reassemble until she is running on her own then I will put it back together for a final time. They only can only come apart and go back together just so many times before it truly becomes a custom install. I have more than adequate fuel pressure I read the response from the guy with the bee in the fuel line/filter. I thought hell that could happen so I bought another fuel filter it should be here in just a couple of days now. While I was at it and while it was primed, i cut the fuel line at the throttlebody and watched it shoot across the shop. Yep that’s fuel pressure right there. I have filled the barrells up , both of them at the same time with one charge, washed the cylinder walls down with that episode. Gonna have to change your oil kind of smells like, well like a gas station On the dipstick. And I’ve had cars and trucks with a fuel injection run out of gas and they always Spit sputtered and stumble as they sucked the last Drop a fuel while sucking air the same time. What they don’t do is go running-dead!!! And I emphasize dead as absolute, not another turn of the crank until I killed the battery turning it over by the key. But I do appreciate your input. It’s the ones that told me after I had changed it out the fuel pump by myself But I thought that it wasn’t the fuel pump but didn’t offer to lend a hand during that process but sure had an opinion about it after it was all strap back in place.
She did have a full tank of gas and by the time I thought well that’s got to be the bottom of it because I swallowed almost half of that! that should be good enough, only to realize that I still had about 10 to 15 gallons of fuel still left in it! I am so glad I took my friends offer to haul off his old transmission jack which I restored because I like junk and the challenge because without that jack I don’t know what would have happened. smash flat probably. Boy I’m here to tell you once that sloshing starts there is no controlling it unless you have it strapped down to the top of a transmission jack. I couldnt imagine having to do it with it just a regular jack, I have enough smash fingers and toes even think about that. And with fuel in it? Jesus.
I’ve taken care of two replies here I don’t deny it but I can almost confirm it, fuel supply is not the issue right now, gotta be logical and the grounding should prove it and that I can start it with the key or my remote starter.
 

Ed Hardy

Newbie
Joined
Dec 23, 2020
Messages
47
Reaction score
21
Location
atlanta
Did we ever get verification on power at the ecm and pulse signal at the ecm during cranking?
I have 12 volts at the injectors I also have 12 V at the ECM. The only wires are grounded out or shorted is the gray wire. It doesn't go to the distributor it goes to the well your safety switch to the tank fuel pump and they fuel switch relay. That's the only one I could fine except for the black and and they are supposed to be grounded. The fuses or sound the only time they blow it when I ground out the injectors and the one that blows is the ECM 1 fuse. I tried running straight wire over there no avail it's not getting the pulse. whatever causes the pulse is not doing it job. Which makes me leery of installing a brand new ECM im not certain that I have found the issue on.
 

Ed Hardy

Newbie
Joined
Dec 23, 2020
Messages
47
Reaction score
21
Location
atlanta
While I feel your frustration, the more I see of this thread the more I suspect a defective or failing fuel pump. Many members here have had brand new ones fail. The fact that it runs when you pour gas in it tells you something for sure. Also someone mentioned the possibility of a security system shutting off fuel. Have you adequately tested for that? Everyone here wants you to get this beast going and when you do it is going to be something simple and likely a face palm moment. Good luck!
I have found no alarm system no cobra no bulldog nothing like that this this truck didn’t even have key fobs. But I have come across shopping kind of interesting. The ECM up all over eBay has a chip the problem chip for the transmission is a Z one industries Prachya looked it up I’ve attempted rather and she seems to be kind of a hush-hush kinda hush hush. It’s made for my truck I’ll send a picture. Now to have that exact Ailment on two different ECM‘s both not having a Pulse what do you think about putting a brand new ECM unit in it and have the same issue? I know what I’m hear next, all together at the same time now, “why didn’t you buy a scanner instead of buying a new ECM”? I didn’t have enough for that damn thing that’s why I got The ECM I don’t know how to operate the damn things. I don’t know what I’m doing To begin with. At my luck I would buy POS off a eBay or something and think that I broke the thing I don’t know , but either way I’m stuck with another boat anchor. So I’ll just blindly sling money at it Until it runs.
 

User_name

T.B.I Guy
Joined
Mar 19, 2022
Messages
277
Reaction score
461
Location
Mississippi
Now here's a thought.
I've seen aftermarket remote starts and aftermarket anti theft systems cause all sorts of stupid and impossible issues
 

User_name

T.B.I Guy
Joined
Mar 19, 2022
Messages
277
Reaction score
461
Location
Mississippi
And I promise if you buy a scanner and learn to use it you'll be less likely to have a heart attack over your truck.
YouTube and Google can teach you to use it. You fired the parts cannon and spent what seems to me like thousands of dollars on parts that got you nowhere. A used snapon solus or hell, even mt2500 can be had on ebay for 450 dollars or less.
My suggestion is quit crying and get a scan tool. Play with it. Learn it. And report back with data from the scanner. Then we can look at the data and tell you something with more certainty instead of all of us sticking our ***** in blind holes.
Sorry if I offended but the truth hurts. Stop being afraid of technology. It can help you if used correctly.
 
Top