Does this sound like a bad IP???

[nate_o23]

My 85 Suburban Is a real pain to start cold. I have already replaced the glowplugs and controler with no noticeable effect. It also has new batteries. If it hasn't been driven in awhile it takes a LOT of cranking to get it started, but it fires right up the rest of the day. I know that a bad IP pump can let air leak in and make starting hard. Do you think that is my problem? Is there a way to check/test the IP before I shell out the bucks to have it rebuilt?? Thanks for any help.

[john8662]

Check the usual suspects too.

How long as it been since the fuel filter has been serviced?

The issue you're describing does come from a leak in the fuel system somewhere, that allows air to bleed into the system, which makes the initial starting difficult.

If the injection pump is leaking causing the hard start, then you'll smell diesel fuel at times. You will get a hint of it when popping the hood of the truck when hot. Carefully look at the injection pump to determine if it has any wet spots, the usual suspect is the throttle shaft, so look for weeping along this area.

Besides the pump, it can be cracked hoses either going to or coming from the fuel filter and then going to supply the injection pump.

[nate_o23]

I have changed the fuel filter recently but I have not checked the hoses & IP for seepage, will do that next. Thanks

[nate_o23]

One other thing I forgot to add that makes me think its the IP. When I first start cranking on it, no white smoke appears at the exhaust and the engine doesn't even try to catch. After I have cranked for awhile (15-25 sec)white smoke starts to appear and the engine starts to catch and sputter. After some more cranking it will finally start up.

[wthif]

Still sounds like air getting into the system. So much air that the IP drains some, but with out the engine running it will take some time for the wite smoke to make it out the tailpipe.

[Tatraplan]

Do You have the mechanical lift pump? My 6.2 starts
a lot easier since I've replaced the lift pump for
a new one (i.e still mechanical). It also improved
acceleration a little, even though the old pump did
push some fuel.

/Robert

[john8662]

IIRC in '87 the lift pump was updated to incorporate a check valve to keep fuel from returning to the tank. I haven't had any problems with previous fuel pumps. Just know that when I price a new AC-Delco pump that I tell them that I have an '87 rather than an '86.

But in all reality, if all the connections are tight and the injection pump isn't allowing air into the housing to leave the pump, you shouldn't have a problem with fuel returning to the tank via the supply line. I can see that having the updated pump (if it was really updated to begin with) could help in bleeding a completly dry engine.

Any raw diesel fuel smell under the hood? Usually noticeable when hot after letting the truck sit a little then popping the hood. If you've got a fuel leak then the smell of fuel will be pronounced even if you can't see a wet spot.

J

[doncannon]

Hello All,

I know when I replaced my injectors a couple were leaking at the lines therefore the engine sounded like a couple of cylinders were not firing and ran rough.

just my 2 cents,
Don

[nate_o23]

Well it might not be the IP after all. I was poking around some more this weekend and I found something I did not want to see. I have always had problems with the radiator leaking despite several attempts to fix it. This weekend I filled the recovery tank with coolant, went on a trip, and when I stopped I left the engine running and popped the hood to check the level in the rec. tank. Well the tank was full to the top and there was a steady stream of bubbles. :( Im thinking a blown head gasket. Would this cause the symtoms I described in my first post??

[john8662]

Blown head gasket causing hard starting?

I'd say yes to this one, because you will have low compression in the affected cylinders.

One more trick that hasn't been mentioned to diagnose air in the lines is to install a piece of clear tubing on the fuel return side of the pump. There is a line located on the top of the injection pump that returns fuel back to the tank. You can purchase clear tubing at a local hardware store. Install a piece of this tubing in place of the existing return line. The next startup after install (after it had been run once) see if you can see any air bubbles or if the hose drains at night. If you get lots of air bubbles after the start, then you're getting air into the system somewhere (pump, lines, etc.)

[ZZ]

Yep, his truck seems to have two issues.

Fuel leak down
blown head gasket and/or cracked head.