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Power surging soon after startup, stops after a minute - high idle problem?

Discussion in '1982-Present GM Diesel' started by Quack_Addict, Nov 10, 2002.

  1. Quack_Addict

    Quack_Addict 1/2 ton status

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    I have a 1987 3/4 ton Suburban that originally had a 6.2L in it. Due to the previous owner's neglect, I recently removed that engine and installed an almost new 6.5L naturally aspirated.

    The engine basically began starting and running excellent, aside from the fact that it always seems to start up like it's missing on one or two cylinders. It runs better after a couple seconds and runs great after warmed up. Now that it's gotten a little colder out, I have been running into some problems starting it when it's below about 35 degrees. The engine starts up, blows thick white smoke (kinda looks like Cheech and Chong), and most recently the engine starts to surge massively for about the first minute or so.

    When the engine starts, it doesn't go to high idle on it's own... I have to give it a bit of pedal when it's running to get it to high idle. Lately, the engine will go up to high idle for maybe a second or two, then it starts power surging from about idle speed up to what sounds like half throttle or more. Sometimes the engine just all together stalls - in Park with no load on the engine. It does this for a minute or so, then it's fine for the most part. When I first start to drive the truck though, the throttle is VERY touchy - barely touching the go pedal throws you back in the seat almost like you're trying to do a hole shot. Again, this goes away after the engine is thoroughly warmed up. One observation that I question the meaning of is the driver's side exhaust has oily soot inside the pipe, while the passenger's side pipe has only dry soot in it.

    I don't know if these are signs of an injector pump going out, something with the injectors, a high idle solenoid or what the heck.

    Until a couple days ago, I was running straight fuel, no additives. The last tank full (40 gal) I added about 16oz of Power Services additive and the engine seems to idle smoother, but I haven't cold started it since putting in the additive.

    Any ideas?
     
  2. imiceman44

    imiceman44 1 ton status

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    I would definitely check the glow plugs.
    And I was going to suggest the additives but I see you already did that.
    I use the additives all the time, my engine runs smoother now.
    and the glow plugs will make the start easier and smoother.
     
  3. AgDieseler

    AgDieseler Certified Scrap Producer Premium Member GMOTM Winner

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    That sounds similar to a problem I recently experienced. Most of the time, non-persistent surging in our engines can be attributed to air in the fuel line. While additives are important, the problem of bad diesel would be a persistent one throughout the run time of the engine while using that fuel.

    There are two usual suspects for air in the lines. First, and depending on its age, the fuel filter (Stantadyne box style). The rubber O-rings can become cracked and leak a tiny bit. Second, the mechanical fuel pump. If it's an AC Delco with low miles, then it's not too likely. In my experience, any other brand is a polished turd.

    The filter is available through most any parts house, but I know that NAPA sells Stantadyne though they call it by their house name, Wix.

    What I did to fix my surging problem:
    Based on the fact that my original fuel pump lasted 270,000 miles, I concluded that my 40,000 mile Delco pump was most likely not the problem. I changed the box filter, and all is good.

    Hope this helps,
     
  4. Quack_Addict

    Quack_Addict 1/2 ton status

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    This previously mentioned problem is really getting the best of me now. This morning, I fired up the Suburban with an outside air temp of approximately 20-25*F. I had to pedal the throttle to take the engine up to high idle to smooth out the idle... then I walked into the house to let the Sub warm up. By the time I hit the front door, the engine was surging wildly.

    The truck has sat with occasional starts since November here in Michigan; I put it up for the winter with a full tank of fuel with additive.

    I shut the engine off, then it started right up, no problem, no surge. I let it idle another 10-15 minutes before putting it into gear.

    I was pulling a small boat & trailer, maybe 2000 lb overall weight. As soon as I pulled out of the driveway, the engine kind of hesitated, then took off like a champ when I hit the pedal a little... leaving a white cloud behind.

    I drove the Sub approximately 130 miles on the highway... burned about 1/2 a tank (20 gallons /forums/images/graemlins/crazy.gif) of fuel on a trip that normally wouldn't even move the gauge a 1/4 tank by last year's standards. When I exited the highway and hit some traffic lights, the surging came back... this time on acceleration. With steady pressure on the pedal, the engine would surge from what seemed like dawging to WOT.

    I reached my destination and went to launch the boat, the engine stalled backing up. It fired right back up with a touch of the key. Then it ran kind of like crap, surging and running irregular.

    I parked the truck. About 4 hours later, I keyed the ignition after the glow plug light went out and it fired right up. I had the typical white smoke I have become accustomed to with this engine. The engine seemed to idle fine, so I got out to check the trailer setup before pulling the boat. I got to the back of the Sub and it stalled. The engine is an absolute NO START now.

    I am going to drive back up with my 3/4 ton truck & trailer tomorrow on a recovery mission. Unfortunately I did not have all the tools I wanted earlier to try to diagnose the issue on the spot. The engine is acting like it's got no fuel - it's not even trying to fire on its own.

    One thing I have noticed is that it appears I have fuel draining out of the Stanadyne style fuel filter / separator as the truck sits for a prolonged period of time. Even so, I have started air locked 6.2's in the past and used the same tricks here - no go.

    I haven't got a clue on this one... the fuel filter seems a likely culprit (as it leaks as it sits), but a lift pump or injector pump isn't out of the question in my mind. Fuel... maybe a contributor but not a cause.

    /forums/images/graemlins/1zhelp.gifAnybody help??? /forums/images/graemlins/1zhelp.gif
     
  5. Tybee

    Tybee 1/2 ton status

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    [ QUOTE ]
    One thing I have noticed is that it appears I have fuel draining out of the Stanadyne style fuel filter / separator as the truck sits for a prolonged period of time. Even so, I have started air locked 6.2's in the past and used the same tricks here - no go.

    [/ QUOTE ] Fix where its leaking its probably sucking air in also.
     
  6. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    [ QUOTE ]
    One thing I have noticed is that it appears I have fuel draining out of the Stanadyne style fuel filter / separator as the truck sits for a prolonged period of time.

    [/ QUOTE ]

    I ain't no expert, but I think you got air somewhere and I think you have answered where....
    It don't take too much. You could have an injector that has air in it that won't let it do its duty.

    IN AN EMERGENCY: I would unhook the glow plugs or the relay and put a TINY amount of ether in the air tube. Do not have your glow plugs going when you do this, unless you like blown engines. I started a 6.2 with no glow plugs in the dead of winter with ether for a good 3 months. /forums/images/graemlins/eek.gif
     
  7. arveetek

    arveetek 1/2 ton status

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    Here's my observations:

    1. Surging at startup, usually going away after a while = air in the injection pump.

    2. Excessive fuel consumption = most likey fuel leak, which would also allow air into the injection pump.

    3. Leak behind fuel filter base = allows air into system, causing surging and starting problem.

    4. Excessive surging, touchy throttle, stalling, and then finally no start = could be injection pump failure, but, coupled with the above symptoms, I would suspect a fuel system problem before the pump. I would replace the fuel filter base and fuel lift pump very first thing. At least replace the lift pump....they're cheap. A bad lift pump would explain why you can't get it started at all now. I'll bet once you replace the pump and fix the fuel leak (perhaps bypassing stock filter base with temporary inline filter to check system out), your starting, surging, and stalling problems will go away.

    Casey
     
  8. 82K5_6.5L

    82K5_6.5L 1/2 ton status

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    hey i have the same situation almost.. the previous owner put in a new 6.5L because because the old owner trashed the 6.2, so the 6.5 has about 40k miles on it, besides that, in the mornings when i go out and start it up, it idles high..but when it gets warm it goes to normal u know..so i can hear the loud idle inside and when it goes down i know its times to go..but sometimes at school i will start it up and have to hit the gas pedal and then it idles high and drops back down.. im thinkin its doing this cuz its warming up u know?? well....??
     
  9. arveetek

    arveetek 1/2 ton status

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    As far as the high idle is concerned....

    There is a plunger style solenoid bolted to the front of the injection pump that simply pushes down on the throttle lever to raise the idle rpm up when cold. As these solenoids get worn, they no longer have the power to push the throttle open by themselves, requiring that you tap on the throttle to open the solenoid, and then it will continue to hold the idle up fast.

    The solenoid on my '81 will never push the idle up by itself...I always have to tap the throttle to get it to engage. However, I've driven other trucks where it would work without touching the throttle. Nothing to be concerned about, really.

    Casey
     
  10. Quack_Addict

    Quack_Addict 1/2 ton status

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    I replaced the lift pump ($13 part) and the box style fuel filter yesterday. The old lift pump did not seem to make any suction when I worked the cam lever by hand - the new one wanted to suck my thumb into the inlet when I did this. Also replaced a length of fuel line that I thought was questionable near the tank. I purged the fuel system of air, using a vacuum pump to suck fresh fuel up into the fuel filter as there wasn't any fuel in the line between the tank and filter. I cracked all 8 injector lines and purged the injector pump and lines of air. The engine started up without much trouble. I noticed it didn't blow the huge cloud of white smoke when I fired it up, giving me the impression that everything was in good order now.

    Today, I went out and tried to start it - outside temp is about 55 F or so. After the glow plugs turned off, the engine started right up, idled fairly normal for about 2 seconds, then started to miss and ultimately stalled over the course of about 15 seconds. During this time my neighbors probably thought my house was on fire due to the huge, choking cloud of white smoke. I could not get the engine to go up to high idle, even by pressing the pedal when the engine was running. I got it started a time or two after this, but it stalled every time. It's a no start again. It seems I'm back to square one now...

    There aren't any fuel leaks evident under the truck, however that doesn't rule out an air leak that may be draining fuel back into the tank. I have to go out of town for the day and won't have a chance to get back on it until tomorrow afternoon. I'll keep you guys advised of my progress.

    What can I do to get rid of an air leak in the fuel filter / water separator if this is still a culprit??? I think I've got another filter base around the garage from when I did the engine swap. It's a Stanadyne box filter style but it mounts on the back of the intake - and I really don't want to re-route wiring and fuel lines.
     
  11. arveetek

    arveetek 1/2 ton status

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    Yep, you've still got an air leak. The fact that the engine started and then stalled, shows that there was fuel in the pump, and then it got air into it. I'll bet once you've bled the lines again, you can get it running and it will probably stay running until it's parked overnight again. Then air will get back into the system.

    Problems like this can be tough to crack. I'd trace every square inch of rubber hoses and steel lines. Also, how much fuel is in your tank right now? Could be a suction problem inside of the tank. I know of one guy who ended up getting a bucket of fuel and drawing out of it to help determine if his problem was by the engine or back by the tank. If it runs fine out of the bucket going through the filter, more than likely the problem is back by the tank.

    There is a possibility of having a crack in one of the hard lines running down the frame rail. You may not see a leak, since the fuel might drain back to the tank, and when the engine is running, the lift pump will keep sucking on the line, drawing in air and not allowing fuel to drip.

    Good luck my friend!

    Casey
     
  12. Quack_Addict

    Quack_Addict 1/2 ton status

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    I'm going to check all the hard lines tomorrow when I get a chance. I will likely just replace all the fuel line from the tank to the lift pump this time. Peace of mind, if nothing else. The hard line from about the back of the front door to the engine is currently all original. I installed new rubber line from the top of the tank to the old steel line the other day.

    What are the chances that the leak is up near the box filter element - ie around the gasket? I did have a fuel leak in the past dripping from this area - haven't noticed a fuel leak since installing the new filter the other day, though. That doesn't mean that air isn't getting in and displacing fuel though.

    Hopefully I can get this all wrapped up tomorrow. I'll update in the evening.
     

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