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Hard start/surging **UPDATED**

Discussion in '1982-Present GM Diesel' started by BigBluOx, Oct 23, 2002.

  1. BigBluOx

    BigBluOx 1/2 ton status

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    /forums/images/graemlins/1zhelp.gif My /forums/images/graemlins/burb.gif has developed an interesting new problem. It has become hard to start - I have to nearly hold the pedal to the floor to get it to start. Once it starts (if it will stay running), the idle 'surges'. It does go away after I've driven it down the road a bit - but once I shut it off, the problem returns. My first thought is a bad lift pump or air in the fuel lines. Am I anywhere close? I'm really hoping to not have to walk the 5 miles to work. /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif PLEASE?

    Jon /forums/images/graemlins/burb.gif
     
  2. imiceman44

    imiceman44 1 ton status

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    Re: Hard start/surging

    My guess would be either water or air in your lines, or it could be carbon or soot deposit on the chambers.
    Check your fuel filter and add some cetane and fuel conditionners and see what happens.
    You should always use those additives now anyway because of the low sulfur fuel, that's what I learned recently, and my engine runs much better now that I do use them.
     
  3. arveetek

    arveetek 1/2 ton status

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    Re: Hard start/surging

    Yep, classic symptoms of air-locking, caused by either bad lift pump, or cracked rubber fuel lines. If it started all of a sudden, I'd check the fuel lines from the lift pump back to the tank. Any crack in the lines, and the engine will suck air instead of fuel.

    There could also be a leak in the lines from the pump up through the filter and into the injection pump. Check 'em all.

    If all the rubber hoses look good, go ahead and replace the lift pump. It's cheap. If you want some tips on replacing the pump, let me know.

    Casey
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Re: Hard start/surging

    Funny this should come up.......My 83 did the surging thing for the first time last week. It was cold out and the truck hadn't run in a couple of days. It started okay but it surged at high idle for the first 30 seconds. After 30 seconds it stabilized and ran fine.

    I wasn't that worried until it happened again a couple of days later. Like I said, after about half a minute the surging goes away.

    Well, just for kicks I went outside and started the truck. It hasn't run in four days and the temperature is about 2'Celcius(35' Farenheit). It caught fine and and didn't surge...... Hmmmmmmm /forums/images/graemlins/rolleyes.gif.

    I guess I'm not much help, eh? /forums/images/graemlins/tongue.gif My guess would be air in your fuel lines somewhere. The same kind of surging happens when I swap out my fuel filters- any leftover air in the fuel system makes the engine surge while it works it's way through.
     
  5. BigBluOx

    BigBluOx 1/2 ton status

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    Re: Hard start/surging

    Thanks guys, I'll definitely check those things out. It is very similar to post fuel filter change surging, but it lasts longer. If it helps, it started happening after driving 30 miles (truck was running/starting fine), stopped at a store (truck still started/ran fine), then went to a costume shop for my daughter (about 2 miles away). The truck sat for about 15 minutes (maybe 20), and I encountered the problem upon trying to leave. The average temp was about 45 degrees F. The problem does not exist if I restart the truck in less than around 15 minutes. My truck is started 3-4 times a day on weekdays, sometimes less, sometimes more on weekends (depends on the wheelin' trip /forums/images/graemlins/wink.gif ). I last changed my lift pump about 3 years ago. The block is about 2 years old (GM crate motor) and I know the injection system was carried over from the old motor, but I don't know if the lift pump was. Besides clear tubing on the return lines, is there any easy way to check for air leaks in the rest of the system?
     
  6. Muley

    Muley 1/2 ton status

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    Re: Hard start/surging

    I would have to say that if air is getting in the lines, then fuel is probably leaking out somewhere. I would start by looking/smelling for a fuel leak.
     
  7. BigBluOx

    BigBluOx 1/2 ton status

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    Re: Hard start/surging

    /forums/images/graemlins/grin.gif I finally got a chance to crawl under the 'Burb last night after work. I followed the trail of 'wet' mud up my front axle breather to find either the lift pump leaking or one of the hoses leading to it (the one that sits at the lowest point closest to the crossmember- is this in or out on the pump?). A big thank you to all the advice offered!! /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif I would definitely like to hear the tips for R&Ring the lift pump since it is in a tight place (it almost looks like it's sitting on the crossmember /forums/images/graemlins/shocked.gif). Again, I and my /forums/images/graemlins/burb.gif thank you in advance!

    Jon /forums/images/graemlins/burb.gif
     
  8. arveetek

    arveetek 1/2 ton status

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    Re: Hard start/surging

    I haven't changed a pump in a 4x4, but these instructions should apply just the same for any GM diesel truck with the model 80 rectangular fuel filter:


    First, drain the fuel filter. On the very bottom right side of the fuel filter assy. is a little plastic valve. Right under this valve should be a barbed hose fitting pointing straight down....it will be hard to see, you can feel it though. There might already be a length of hose attached to this fitting. If not, get a length of hose to help drain the fuel away from the truck and into a pan or something. You don't have to, but it will make a much cleaner job.

    On top of the fuel filter assy. is another small plastic valve directly above a smaller barbed fuel fitting pointing straight out on the left side. This is the air bleed valve. Open this valve, and then open the drain valve on the bottom. This will let the fuel drain out of the filter, down the hose, and into a pan. This will prevent fuel from spilling all over you when you remove the pump.

    After the fuel has drained, start removing the pump by disconnecting the fuel lines. The suction side will have a rubber hose and clamp, the pressure side will have a steel line screwed into the pump. Use a 9/16" line wrench if you can to avoid stripping this fitting. When you remove the suction hose, it may continue to dribble fuel out. If so, shove a 3/8" bolt into that hose to stop it up.

    Next, remove the two mounting bolts holding the pump on. IIRC, you need a 1/2" socket for this. The bolt on the back side of the pump is hard to get to. You can try getting to it from the top side of the motor or from the bottom. I think the top side is just a bit easier.

    Remove the pump.

    Now remove the plunger rod cover by removing the two remaining bolts at the bottom. IIRC, these require a 7/16" socket. You have to remove this plate in order to remove the plunger rod. When you removed the pump, the rod probably fell down. Now you can't get the rod to stay up in place. (This rod rides against the camshaft, which in turn rides against the pump plunger.) Once you remove the cover, slide the rod out. Cover it with thick grease, and shove it back up in the hole. The grease will help hold it in place. There is a chance that the motor shut off in a place where the camshaft lobe is holding the rod out in the extended position. If this happened, it will be next to impossible to install the pump. I suggest you rotate the engine by putting a large socket on one of the front pulley bolts. You can tell when the rod is retracted all the way because it goes way up in there out of the way.

    Clean up the surfaces on the rod cover and the engine block. I like to use Ultra Copper silicone sealant on these parts. Reinstall the cover.

    The pump should come with a gasket. I typically install the gasket along with Indian Head gasket Shellac.

    Install the pump.

    Reconnect the fuel lines.

    Now you have to bleed the fuel system. First, if you haven't recently replaced the fuel filter, go ahead and install a new one. Just undo the clasps and pull straight out on the filter. Put a little oil on the o-rings of the new one when you go to install it. The new one just pushes back on.

    Close the drain valve on the bottom of the fuel filter assy, but leave the air valve on top open. Next, disconnect the fuel cut-off solenoid on the injection pump. This is the pink wire right on top of the pump itself. We want to avoid pumping any air into the injection pump when we start cranking the motor, and by removing this wire, the air can't get into it.

    To save battery power and the glow plugs, disconnect all 8 wires going to the glow plugs. (If you have an automatic glow system...if yours is manual, then just don't glow!)
    If you can, install a piece of clear tubing over the small barb on the top left of the fuel filter assy. I usually run this clear hose into a container sitting on the cowl of the vehicle so I can see it from the driver's seat.

    Start cranking the motor over. We're not trying to start it, we're just priming the system. What you're doing is pumping fuel from the tank, into the pump, up to the filter, and back through the return lines. Since the injection pump is disconnected, it won't get any air in it and get air-locked.

    Only crank the motor for no more than 30 seconds. I have personally burned up a starter by cranking too long. Let the starter cool for 2 minutes before cranking again.
    When you see clean diesel fuel coming out the hose at the top of the fuel filter, shut the air bleed valve off, disconnect the clear hose, reconnect the pink wire to the injection pump, reconnect the glow plugs, and start it up. I guarantee it start up on the first try with this technique.

    I know this seems like a lot of steps, but you should be able to get this all done in under 2 hours. I can do it now in under one hour. Using these steps makes it very easy to change the pump and bleed the fuel system.
    BTW...you can use these same steps to change the fuel filter. Just skip the part about changing the pump!

    Good luck!

    Casey
     
  9. arveetek

    arveetek 1/2 ton status

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    Re: Hard start/surging

    BTW....

    The rubber hose going from the frame rail to a barb on the fuel pump is the inlet or suction side. The hard line that is screwed into the pump goes up to the filter and is the output or pressure side.

    Casey
     
  10. BigBluOx

    BigBluOx 1/2 ton status

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    Re: Hard start/surging

    Many, Many Thanks! /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif It went very smoothly, and my BigBlu /forums/images/graemlins/burb.gif is running like it used to!! I did notice that the low pressure side of the pump (the hose itself actually) does rub on the crossmember, so I ended up replacing that length of hose as well. I am wondering if I have a motor mount problem as well (it doesn't seem like the engineers would put it that close). In the meantime, the truck runs beautiful /forums/images/graemlins/grin.gif. If you're ever in Bellevue, Washington State, let me know. I'll buy ya dinner or a beer. Thanks again

    Jon /forums/images/graemlins/burb.gif
     
  11. arveetek

    arveetek 1/2 ton status

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    Re: Hard start/surging

    Glad to hear you got it fixed!

    The motor mounts are also another weak area of the GM diesels...they take an awful lot of abuse from the strong pulses and vibrations of the diesel. They're same mounts as used on the small block gassers, so no wonder.

    I had to replace the right motor mount and rear transmission mount on my C20 a while back. Both mounts were new about 50,000 miles ago. I had noticed the passenger side of the engine was tilted down, and upon closer inspection, noticed that the rubber was totally ruined. The metal mount on the block was actually resting on the metal part of the mount on the cross-member.

    Replacing the motor mounts is not fun. You have to jack up the motor, and pray that the bolts in the cross-member will loosen up. It was probably the most difficult job I've had to do yet on my truck, and I've rebuilt just about everything on that sucker.

    Casey
     
  12. Tybee

    Tybee 1/2 ton status

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    Re: Hard start/surging

    So your saying if I ever change the engine I should change the mounts! /forums/images/graemlins/grin.gif
     

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