Drove about 40 miles, all hwy , to a horrible truck pull. Then went to a place to get boots. Pulled in the parking lot and the truck was idling funny like cutting out. I raced it up and it seems to clear a little. I noticed the speedo was bouncing around a little while it was idling weird. I shut it off and it hesistated to shut off. Went in and got my boots. Came out crank but no start. Opened the bleeder on the FF and it had residual pressue(I was bymyself). No test light but with key on took wire off IP a few times and saw it sparking like it was getting power. Went back in with foot to floor and it finally started as the POS interstate batteries nearly died(Those gotta go).
No smoke that I could see, was still idling bad and had to kepp it raced up a little to keep it smooth. Drove 40 miles home with no problems, plenty of power and it's running fine now. I'm at a loss here. Maybe I should have went to church with it again. I think this thing may see the torch yet. I'm losing patience quickly. Grounds are clean cause I cleaned everyhting up when I had the heads off a few weeks ago. All I can think of is ign switch, LP or IP. When it was idling rough it felt like someone was cutting power to the IP quuickly. Is the IP power looped through the ecm in this thing or come directly from the key ?

Also is the ign switch on the top of the column or is it the white one at the bottom. For some reason I seem to remember that white one at the bottom being the neutral saftey/reverse light and the ign switch being on top of the column and a real C--- to get to.

If it's the same as the earlier ones its the one at the top. safety is at the bottom.

Reading your post a few times something clicked. Maybe the power to shutoff solenoid is funky. That could be why it idled weird, wouldn't shutoff immediately and wouldn't restart at first. Maybe the wire is cooked, give it a few bends and feel for hard spots. Other than that maybe the solenoid itself. Only thng it doesn't explain is the dancing speedo.
After reading again I'm wondering what kind of IP you have. Is it mechanical or electric

its mechanic. 1990 burb. ignition switch has to be toast. its pissing around with you.

Switch is at the base of the column .

Yeah I'm thinking switch too. IIRC the column has to be dropped down to change it no ?
It has Mech Ip.

Yeah I thought it was mechanical. The reason I asked was your comment about power for the IP coming through the ecm. If it was the ignition switch would it idle rough like that? I thought that just opened to start the vehicle but now that I'm writing it I see that it also has to close to shut the vehicle down. That makes more sense

Nope , it has 2 small bolts/screws holding it to the column . Watch the neutral alignment .

Well unless it's internal to the IP it's not the ign switch. I got a feeling the IP is junk. I went out just before and it would not start . Just cranked and cranked. I ran a jumper from the batt to IP and same thing. it finally started after cranking with my foot to the floor and was idling rough like it lost prime so either the LP is shot or the IP is shot. I looked along the chassis and saw no evidence of fuel line leaks. Given the shut off issues I'm starting to think the IP is NG but i throw an Elec LP on it tommorow and see. I wanted to do that anyway. I think the speedo jump was a fluke. Once it was running I opened the bleeder on the FF. It came out but wasn't flying out. More like a weak stream while running and truck did not stall. I'm gonna be pissed if that IP has to come off again.

Try putting a voltmeter on the pink wire at the IP and see if it fluctuates. Do it with the power from battery to eliminate power from truck problems. I don't know if the shutoff solenoid is replaceable but...

I guess that last suggestion doesn't really make sense. I'm absolutely terrible with electricity, but there must be a way to test the shutoff solenoid

Sounds like my blazer when i had a fuel issue, save for the residual pressure. When you opened the bleeder did you get a "hiss" sound or did you have fuel coming out?

Could be a leak pre LP or even at the filter housing causing fuel drainback. When i had a leak at the filter housing i didn't loose fuel when it was running, but it'd have a small puddle under the truck(2-3 inches in diameter) and it would start really hard and onyl if i had my foot to the floor and then it'd idle rough for a bit.

I had already swapped the shotoff with the another IP. Gonna put a stock 93 LP in tommorow and see what happens

If it's a fuel problem why would it keep running after you shut it down?

Could be 2 separate problems. The sutting off problem has been present since I put the IP in. This is a newproblem, they could possibly not be related which would screw with me more and is typical of my luck. I want to do the elec conversion anyway so no loss if it doesn't fix the problem. Just want to rule out all possible causes as well before Crucify the IP.

Good thinking to eliminate easy things first. espescially if they wanted eliminating anyhow.

Yeah, no secret that the factory Mech LP's leave alot to be desired IMHO.

Yeah, no secret that the factory Mech LP's leave alot to be desired IMHO.

I don't like them either after what mine did. Diesel in the oil is a real good way to kill a motor, and you'd never notice short for seeing that the oil's thin and smells like fuel.

Kinda sounds to me like a short in the wiring harness. Is the harness in good condition??
Melted wires under dash?? Check the column, common place for blue wires to melt.
Rubbing on metal at a passthrough in the fire wall??

wiring all looks good and like I said as far as not starting I ran power right to the IP. It wouldn't start this am either .It tried to start then died and then I had to crank the piss outta it with my foot to the floor. I'm thinking drainback. I see oil around the area of the Mech LP as well. waiting for the elect one to come in. Already ran a wire for it.

wiring all looks good and like I said as far as not starting I ran power right to the IP. It wouldn't start this am either .It tried to start then died and then I had to crank the piss outta it with my foot to the floor. I'm thinking drainback. I see oil around the area of the Mech LP as well. waiting for the elect one to come in. Already ran a wire for it.

Yup you've got drainback issues. That's what mine did as well when i had an air leak.

Well, I think I know what the problem is hopefully. So after all is said and done and I was ready to rip the IP out ... The truck is running like total crap banging knocking has a low rpm miss. I installed a New LP from a 6.5TD. No difference. In fact, almost seemed worse. I put a volt meter on the ip ESO and gounded to the IP itself and it read 13.8 consistently even when I revved it up a bit and it was making so much noise I thought it was coming apart. It sounded so bad I actually was thinking some sort of catatrphic failure was taking place. Then I took a minute and thought about it. The high idle has some sort of problem. It's always on so I had unplugged it and it didn't bother me enough to figure out why. I'm not excatly sure what the other wire does that goes to the side of the IP and it tied to the high dile but I think it's some sort of cold advance. I thought , wait if the power is constant to the high idle sol then it must be constant to that too so I unplugged it. Now maybe it's a coincidence cause it's raining and getting dark and I didn't have a chance to hook it back up, but as soon as I unplugged it truck ran much better. All the horrible noise was gone. I drove it around the block and was fine although it seemed to have a little less power but when I drove it home on Sat after it started acting up I noticed it felt weird almost like a gas engine running too lean. So if there is a problem causing constant power to this thing when it shouldn't I'm assuming it has a sensor ?? The truck has an ALDL connector but the pin that you would jump for engine codes is missing and I was told that in this truck all the ALDL is for is the ABS brakes. So what's next ? What does that green wire do on the side of the IP ? would that cause this ?
I'm lost now.

Also when I installed the 6.5 LP the only fitting I could get locally were Fuel line repair kits so I figured screw it I'll splice right into the steel and make it look all factory instead of hack with rubber lines.
These pics are the right way to add a LP.

This si the wrong way(I bought the truck like this..)

Yeah other green wire attached to high idle wire is cold advance. When truck first starts it should help with idle not make it worse. At least it should. You don't need high idle or cold advance, try leaving both disconnected and see what happens.

It runs better but I'd like to know what's causing power to be there all the time. I don't know how it's wired but I'm thinking maybe the sensor is shorted ???

The high idle and cold advance are controlled by water temp, as motor heats up switch opens....can run without, just will be smokier at start up, and run rougher till warm. With power all the time, IP will be too advanced, pinning, rattle and power loss.

pinging, he means, but im sure you figured that out. that still sounds weird why a switch would stick closed like that. usually they stick open and dont work at all.

That is a clean lp install, tried to quote, but having site problems all night when quoting and post reply.....only working correctly with quick reply...:confused:

For what its worth (I know your wiring is probably different) these are the temp switches form my '84. The switch on the top of the pass head is the temp inhibit switch controlling the GPs. the switch on the bottom, behind the exhaust controlls the cold advance/high idle.

as has been said, your fast idle and cold advance is controlled by the temperature switch in the head. After the problems I had with the controller for the glow plugs, I decided to bypass that switch too with a manual switch in the dash rather than replace the switch. Good luck

That is a clean lp install, tried to quote, but having site problems all night when quoting and post reply.....only working correctly with quick reply...:confused:

Thanks. I try to do stuff right..

So today I tried again. It was dying driving up the street like it was running out of fuel. I sight glassed the fuel line going INTO the FFM and at idle it looks fine but under high rpms I see bubbles. I'm wondering if the pickup tube is shot. Also the truck is back to not shutting off. I'm ready to just junk it. That is obviously where it was destined to go. what a POS this thing is. I give up. I'm gonna pull the plates cause I'm outta ideas.It's near impossible to start cold. Glows only cycle for like 5 seconds.

So today I tried again. It was dying driving up the street like it was running out of fuel. I sight glassed the fuel line going INTO the FFM and at idle it looks fine but under high rpms I see bubbles. I'm wondering if the pickup tube is shot. Also the truck is back to not shutting off. I'm ready to just junk it. That is obviously where it was destined to go. what a POS this thing is. I give up. I'm gonna pull the plates cause I'm outta ideas.It's near impossible to start cold. Glows only cycle for like 5 seconds.


be like everyone else, just throw a cummins at it.....lol...:drinking:

They have thier issues too, trust me, I just sold one.

Well, I was ready to rip the IP out and I decided let me go through all the motions cause those air bubbles in the fuel were really bother me. As always nothing can ever be simple for me. Always has to be something no one has seen or more complicated that it should be. The IP has a sticking vavle whic is causing the shut off but the no start running bad is sucking air somewhere in the fuel syste,m which I strongly suspect is in the tank. F'in truck is possesed. I think it wants me to pull the tank so now I can't in good conscience not fix the frame cause it would be easy to do with the tank out. I sight glassed it and it had consistent air bubbles. So I swiped the LP off another truck filled a 5 gal can with fuel and ran clear tubing from the can to the temp LP and then from temp LP to FF housing. No bubbles. Had to crack the lines but once bled it roared to life and ran fine. ran it for 20 mins off the 5 gal can both idling and revving it up. Not one bubble in the fuel. Guess the tank is coming out. Gotta price straps tommorow.

You've mentioned sight glass a few times. What's that?

Using clear tubing for a fuel line so you can see what's going on. It's the only way to know if there is air in the fuel. Make no mistake , air in fuel will make the truck run horrible and sound like it's coming apart. Air in diesel fuel=Bad.

Basically every deisel mechanic should have a temp LP, a 5 gal pail of fuel, and some clear tubing to use as fuel line. I should have done that from the start.

Ok I knew that trick just never heard of it called sight glass. BTW if I wnted to put some clear line on and leave it on, what type of plastic/rubber/synthetic crap should I use?

goldfish aquarium tubing :p:

Ok I knew that trick just never heard of it called sight glass. BTW if I wnted to put some clear line on and leave it on, what type of plastic/rubber/synthetic crap should I use?

Something along the lines of lawnmower fuel tubing.....

Seriously? I guess diesel isn't really a solvent like gas but does anything work?

Ok my last comment was directed at 4320. Lawn mowers use clear tubing? weird

Ok my last comment was directed at 4320. Lawn mowers use clear tubing? weird

They can....... I saw some last time i was in Northern Tool....... They didn't have the size I needed or I woulda got some of that to use when I was checkin for air in the fuel.......:rolleyes: (they were just out at that time)

Using clear tubing for a fuel line so you can see what's going on. It's the only way to know if there is air in the fuel. Make no mistake , air in fuel will make the truck run horrible and sound like it's coming apart. Air in diesel fuel=Bad.

I've been trying to hunt down Tygon clearish yellow fuel line in 3/8" for a long time now. I have permanently put a short piece of clear from the stock hose where the mech LP was to my electric LP on the inner fender. It is nice for checking for drainback and air bubbles.

I've found that the vinyl tubing i'm using now gets stiff when cold and when you tighten the hose clamps onto the bare line it tend to poke small holes in it, letting air in. I wrapped a fresh piece of that clear hose with electrical tape where the clamp was going to go so the clamp "bites" into the tape instead of the hose.

They can....... I saw some last time i was in Northern Tool....... They didn't have the size I needed or I woulda got some of that to use when I was checkin for air in the fuel.......:rolleyes: (they were just out at that time)

Was the stuff you were looking for yellow-ish clear or clear Tygon fuel line? If so and it's 3/8" ID pick some up for me and i'll gladly pay you for it. I can't find it here at all, I've tried.

i was goofing about the fish hose. i dont know if it would swell or not. or just get hard and break from the heat of the valley and crossover right by it.

Ok I thought so but then again you can buy oil in just about any kind of plastic container, but like Dave says they don't get subject to hot and cold and salt and other weird things that engines do

Ok I knew that trick just never heard of it called sight glass. BTW if I wnted to put some clear line on and leave it on, what type of plastic/rubber/synthetic crap should I use?
They are correct, use the stuff that they use on lawnmowers. It is called neoprene tubing. I use it on my returns, it is recommended to use for low pressure fuel supply applications when messing with biodiesel too. If you look in my garage, you will see that I have the yellow neoprene tubing on my engine's returns, purchased from my local hardware store at the parts counter. It works great, does not deteriorate, I like it.

Was the stuff you were looking for yellow-ish clear or clear Tygon fuel line? If so and it's 3/8" ID pick some up for me and i'll gladly pay you for it. I can't find it here at all, I've tried.

Which are you wanting? IIRC they had a spot for both......

AFAIK there is nothing availible for permanent use that I have seen anyway.

Ok if not for permanent use how lon does it last? years I guess

Ok if not for permanent use how lon does it last? years I guess
Mine lasted on my returns for about 5 years. Never leaked- I just quit driving the truck nd pulled the engine for use in my current project. I was so happy I didn't know what to do. Previously, I had nothing but trouble out of the rubber hose I was using. I had replaced it with more rubber hose, it started leaking inside of a year's time. Heard about neoprene, decided to give it a try.

Which are you wanting? IIRC they had a spot for both......

I want some form of Tygon tubing in 3/8" ID. Clear or yellow-ish clear doesn't matter as it's main function is to check for air bubbles.

The Tygon is much more flexible even at lower temps and seals better than the vinyl tubing i'm using now.

I want some form of Tygon tubing in 3/8" ID. Clear or yellow-ish clear doesn't matter as it's main function is to check for air bubbles.

The Tygon is much more flexible even at lower temps and seals better than the vinyl tubing i'm using now.

I'll try an get down there tomorrow and take a look.....

Neoprene. That's interesting. Same thing that cheap yellow rope is made of If memory serves. It can certainly take both hot and cold. Hot to an extent I guess

well I've been tied up with my new Dually project but I finally played with the Burb last weekend. It has a few issues . The hard starting is the glows not cycling long enough. I have no idea why. I changed the temp switch on the pass side head and no change but atleast the high idle and cold advance is working properly again. Guess I need an override. Oh BTW Green Machine was correct in his htread. My GP light will go on when overrode. The jumper I was using was not heavy enough. Ok next issue. I sight glassed it and it was sucking air so I ran it out of a 5 gal can with the spare LP right t IP. NO air in line. So I disconnected the fuel line at the tank and dropped it in the 5 gal can. No air. So I dropped the tank and there is a pinhole due to rust right where the line bends to go in the tank so the sending unit assbly is done. I had to pressurized it in a tub of water to find the leak. So I have a Pureflow fuel tank pickup kit that came with my Raptor that I didn't use. I think I'm gonna chop a hole iin the tank and use that. It's a 1/2 inch PU tube. The factory send unit is over 200$. I bought a roll of Russel Blue anodized aluminum 3/8 fuel line to replace the line on the chassis to the LP. So hopefully I can get all that done but since "Christine" made me pull her tank out I know she wants the frame fixed for future tow hitch.

Well, The frame is junk. I started to fix it with the tank out and then I looked further up over the axle..
So The tank is going back in tommorow and the frame is what it is. Too much to repair and pointless. I'll drive it till it falls in half. It's not that bad and will probably be fine for normal driving but towing is no longer in it's future. Frame was so bad I had to used dumpster rod.

It's ashame cause the repair was coming along good.

thats terrible. must salt like crazy down there. because my truck is a northern truck but they sand the roads here, so my frame only has surface rust on it :D

That frame is a wreck kenny. I still agree with your towing a boat theory. That would explain it.

My blazer's frame isn't that bad, from what i've seen of it anyways. Over by the hitch is a little pitted but it's not like your burbs.

:eek: wow........ that frame just looks horrible...... Looks like the whole back end was just parked in salt water all the time.......

my frame was excellent, till i got to the back end. oil and grease kept the front good. undercoating and salt kept the back rusty. in the front, the undercoat was soft, in the back it was dried out with rust scaling underneath, peeling it. all the road salt collects under here as well. other trucks with paint only frames seemed to fare better

well, I abandoned hope of fixing the frame to make it a tow vechile and decided to just put the tank back in and run it. The sending unit/pickup assby is rotted. GM discontinued it and the few left they want 350$ for. Obscene. LMC gets 200$ for it. I had the pickup tube kit from the Dodge that I never used It needed some mods as thE dODGE uses a plastic ex tube. Luckily 3/8 steel pipe fits nice and snug in th bulkhead fitting so I brazed it and then pressure tested it under water at 70 PSI. No leaks. I also had to very carefully braze a pinhole in the return line tube. So I drilled the tank , bent up the new PU to be similar to the old. The only thing was the access hole in the tank isn't big enough to get my hand in so I could not reinstall the screen. In lieu of that I installed a Holley Glass fuel filter inline coming out of the tank that should catch any debris as good as the screen pre lift pump. Put the tank back up and ran the fuel hose into a bucket until clean air free fuel came out. Then connected and vroomm. I also did the Manual override mod to the glows. No the only issue I can't figure out is why the cold advance/high idle is staying on. I replaced the sensor to no avail unless the new sensor/switch is bad too. Otherwise truck starts good with the override and runs excellent. It sounds 1000x better. Air in the fuel in even the most minscule amount will cause the engine to sound/run bad. I'll keep my eyes peeled for a Blazer/Jimmy/Burb in better shape rustwise to transplant my driveline into

sounds like the Po hard wired the stuff to the keyswitch or theres wires melted somewhere. or in that plug for the sender. or like you said the sender could be bad even though its new. mexico or china just doesnt know wiring anymore.

Kenny trace the green wire for the high idle/cold advance circuit. If it's staying on it's getting power from somewhere that it's not supposed to.

Yeah I have to tommorow. Ran out of daylight.

Yeah I have to tommorow. Ran out of daylight.

Ditto. i have to snap some pics of my sending unit, since i can't get my head up there to see it with my own eyes. Fuel lines feel all nasty and crusty though. :mad:

I changed the SU/Switch a week ago with the new updated one. They no longer make the one with the blades. Had to get the pigtail as well. Still doing same thing. I'll have to test and see if power is getting past the switch in which case...WTF ? Does this site have a suicide smiley ??? We need one badly.