Author Topic: Opinion needed for a 1988 V20 6.2L J code starting issues.  (Read 1522 times)

Offline MuddiGGEr25

  • Registered Users
  • *
  • Posts: 243
  • Wrencher
Opinion needed for a 1988 V20 6.2L J code starting issues.
« on: October 30, 2016, 10:09:12 AM »
Ok, im not sure where to begin on this one... i have the other thread about starting it for the first time in 6 years.


So i got stranded about a week ago 60 miles from where im living right now, that time turned out to be the starter

Ive got new batteries, ive cleaned all the connections including starter terminals while i was down there.

I have this issue whenever i start it for the first time everyday, the glow plugs kick on for 5-20 seconds (by my count) then crank and it will fire up, and the glows will cycle on and off the first 10-15 seconds of idle, but then it will shut off, and wont start up again no matter what unless i use one of the following: WD40 which i ran out of, or propane but now its getting too cold for it to come out of the bottle, or about 1 shot glass of raw diesel either misted or just dumped into either side of the intake (yes i know, not a good idea because diesel is supposed to be a mist and not solid liquid, and risk bending shoot or breaking the starter or hydro lock, etc, i know its risky as Heck so i use it sparingly.

Once the starting aid is in, then if i hold the pedal to the floor while cranking, it will fire right back up, tons of white smoke (smells of diesel) it will rev up, then almost die, and will die if i dont keep the pedal to the floor, but after 3-6 seconds of sounding like it has no fuel it will spin right back up to redline and then i can let off and it stays idling, and its fine for the rest of the day, assuming no more than 2 hours between starts to run errands.

Running a electric diesel fuel pump 4-7psi and rated for 35GPH


I am thinking i am getting air in the incoming side of my fuel pump somewhere because almost everytime i can open the bleed valve and i can get foam or it will spit fuel for a few moments until the stream gets steady again. but then again i have checked the bleed off with the pump running but before ever cranking the engine, and i already have air in the filter so that makes me think that the air is coming in at the filter housing... but there is no evidence of a fuel drip at the filter housing and i have checked all the lines coming in and out. i am going to put some dry paper towels under the filter housing here in a minute after the engine is fully warmed up and wait and see.

Yes the fuel pump has a check valve and i bypassed the mechanical pump since i couldnt get the electric pump to push the fuel past, or atleast it seemed that way.  I intend to put the mech pump on in the spring once its above 30F again unless i can rent  a shop somewhere


otherwise it runs great, it towed 7000lbs up and down some very steep hills and kept between 45-60MPH the whole time. and no i havent turned up the IP yet, just want everything working right first.
1988 V10 Suburban 5.7L TBI/TH350 39K on rebuild 4.10AR GM14FF/GM10SF 235/85R16 & 18.4-16.1

1988 V20 Suburban 6.2L-J/TH400 CA truck, 125K G80 14FF/ GM10 4.10AR GVWR 8,600

1977 Ford Granada ~450HP 302 2bbl/C4 27K original 2.47 215/70R14

Offline hatzie

  • Site Supporters
  • Junior Member
  • ******
  • Posts: 771
Re: Opinion needed for a 1988 V20 6.2L J code starting issues.
« Reply #1 on: October 30, 2016, 11:02:13 AM »
Replace the injector return loops with GERMAN >NBR< braided jacket hose.  The braided hose doesn't need the mini clamps to prevent leaks.  Be sure to cut it straight and square with a NEW SHARP razor blade.
Replace the injector return termination caps with new VW or Mercedes diesel injector terminator caps...  when I ask for diesel injector return caps at a GM dealer I get the dumb stare.
You can buy the caps and braided injector return hose at any VW or Mercedes dealer.  1978-1984 VW Rabbit or Jetta Diesels or late 70's Mercedes 240D use the same style Bosch diesel injectors as the GM Detroit AMG 6.2 L & 6.5 L Diesel engines.

The Stanadyne 80 box filters and bases tend to corrode and leak air around the water in fuel sensor.  I usually replace them with the more reliable and easier to service stock 1995-2001 GM 6.5L Fuel Filter Manager mounted in the back of the intake valley.  You can use any decent spin-on Diesel fuel filter base and filter but the GM unit has heater and water in fuel sensor that's compatible with your truck with some connector juggling.

If your fuel pump connections leak you'll suck air instead of fuel.  If you used worm clamps replace them with German Fuel Injection clamps.  They don't loosen up.
Replace the worm clamp on the return line off the top of the injection pump with a German Fuel Injection clamp.

If you have the original obsolete SAE J30R7 fuel hoses replace them with SAE J30R9 fuel hose.  J30R9 hose is more fuel and fuel vapor resistant...  and it's not 30+ years old.  If the worm clamps chewed up the hose you installed on the fuel pump replace it. 

Check the hose you used to bypass the mechanical pump.  If it's installed with worm clamps replace the hose and the clamps.
« Last Edit: October 30, 2016, 11:09:54 AM by hatzie »
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
Parts & Illustr Books -->http://tinyurl.com/SqParts
GMSTG Textbooks-->http://tinyurl.com/STG-TEXTBK
Radio Manuals-->http://tinyurl.com/DELCORADSVC

Offline MuddiGGEr25

  • Registered Users
  • *
  • Posts: 243
  • Wrencher
Re: Opinion needed for a 1988 V20 6.2L J code starting issues.
« Reply #2 on: October 31, 2016, 11:20:16 AM »
well i tighened all hose clamps... some were actually rather loose, but the one at the hard line coming from the tank i could not find a way to tighten so gotta figure that out (no access with a wrench, ratchet or screwdriver. so gotta find a 12" flexible extension.

This morning, its pretty warm 50F right now, so nothing compared to the -20 to -40 temps we will see this winter ( yes actual temps not windchill), however i cracked open the bleed screw on the filter, it still had pressure, i turned the ignition on so the pump was running, and bled it for approx 10 seconds at which point the flow increased, then closed it and re-cycled the glow plugs and she fired up no problem,

i held the throttle about 1/4 and it did still bog down a bit, but not as much as before then rev'd back up after maybe 5-10 seconds.

I did pick up a big blast can of WD40 yesterday just in case i have any issues as the temps drop back down in the coming weeks. I cant buy any parts until i get back to work (1 surgery, 1 steroid shot, and 1 broken foot this year pretty much wiped out any cash we had saved up)

I will more than likely replace all the clamps like you said, and better hose too, and going to change the oil and fuel filter at that time too. the oil is ok for now, i drained 1qt and added 1qt lucas HD oil stabilizer. i know there are varied opinions of it, but i have run lucas, marvel mystery oil, and usually mobil 1 full synthetic in everything i have owned, and i beat on my vehicles hard, as in towing at max or sometimes a little over, or drag racing at the airport or mud drag races competing in the local group, or mud bogging, basically everything i do puts my vehicles under strain and redline more often than not, and i have never had an engine failure due to the oil, yes overheating, and sometimes a axle shaft or some other hard component but never a catastrophic engine failure. ( unless i picked up a $200 car/truck)


ok enough rambling from me. ill update this post once I get a paycheck and go buy parts
1988 V10 Suburban 5.7L TBI/TH350 39K on rebuild 4.10AR GM14FF/GM10SF 235/85R16 & 18.4-16.1

1988 V20 Suburban 6.2L-J/TH400 CA truck, 125K G80 14FF/ GM10 4.10AR GVWR 8,600

1977 Ford Granada ~450HP 302 2bbl/C4 27K original 2.47 215/70R14

Offline MuddiGGEr25

  • Registered Users
  • *
  • Posts: 243
  • Wrencher
Re: Opinion needed for a 1988 V20 6.2L J code starting issues.
« Reply #3 on: November 10, 2016, 10:03:54 AM »
Hey Hatzie  do you know what the specs are for the volt that goes into the block on the starter brace? Mine arrived today and I can't seem to find the bolt I took out anywhere.... imagine that lol.

 And my micro vacuum pump arrived today so now my th400 will shift properly lol and I'm hoping the cruise works.  I'll have to figure out something long term or a way to conttol the pump when vacuum is high enough. Or just buy spares lol they are only 12
1988 V10 Suburban 5.7L TBI/TH350 39K on rebuild 4.10AR GM14FF/GM10SF 235/85R16 & 18.4-16.1

1988 V20 Suburban 6.2L-J/TH400 CA truck, 125K G80 14FF/ GM10 4.10AR GVWR 8,600

1977 Ford Granada ~450HP 302 2bbl/C4 27K original 2.47 215/70R14