1984 Chev one ton military pickup truck w 6.2 diesel engine

I don't know if this is the correct group to post this to. If it isn't then I appologise and hope someone will be kind enough to point me in the right direction. We have this truck which had a badly leaking fuel tank. We replaced the

tank and have been able to get fuel up to the filter but we are not certain if it is getting any further. We opened one of the injector lines while the engine was cranking and did not get any air or fuel out

of it. I was told that we should open all the lines to bleed the system

of air. How important is it to do this? Will the air eventually be pushed out into the cylinders if you don't? And when bleeding, do you do this one line at a time or all together? We are hesitant to try to open a number of these lines because they are so badly rusted I'm afraid we may break them off. Is there any other way to do this, perhaps by pulling the glow plugs? Will that bleed the air out of the lines? Also could someone please tell me something about how this injector pump works, and how to confirm if it is working properly independant of wether or not it will start the engine? I understand that it is something like a distributor which runs off the cam but instead of distributing spark it distributes fuel? I think I have alot of blow by because the oil gets very dirty and thin

very fast. I also think the glow plug controller is operating off the breaker system which is a backup because of voltage readings from last fall told me that it wasn't working the way it should but still worked off the backup. The truck wont fire up. I have pulled the glow plugs and I dont know if a problem with the fuel not geting to the cyclinders

or compression? Maybe the glow plugs are not working enough to heat it up. Maybe the batteries are not strong enough to turn the engine fast enough because it doesnt seem to crank very fast at all even with 3 batteries fully charged and the block heater plugged in for hours it still did not crank fast. Does it need to crank fast to start? Thanks in advance. Lenny

Reply to
captainvideo462002
Loading thread data ...

Wrong group, but here goes. Remove the glow plugs to reduce compression. Slacken one injector delivery pipe and turn the engine over, you should get some air bubbles then just clean fuel, repeat for each injector. While the glow plugs are out connect each one to battery power and make sure it glows nicely after a few seconds, replace any that don't. Refit glow plugs and start. Further diagnosis requires equipment beyond amateurs (in very general terms)

Diesels need lots of compression and good cranking speed or they won't go.

mrcheerful

Reply to
mrcheerful

The message from snipped-for-privacy@yahoo.com contains these words:

Very and yes.

Assuming you've got fuel as far as the injector pump[1], then while someone is cranking the engine slacken the fuel pipe nut on each injector in turn until fuel soaks into the rag you've cunningly wrapped round the joint. Then tighten it and move on to the next.

There are such things as self bleeding engines, but in my experience they don't always manage it. What's happening is that the pump shoves fuel up the pipe expecting it to lift the spring at the other end to allow it to get into the engine. If there's air in the pipes then that compresses instead and the fuel just gets pushed back into the pump later.

[1] Find the bleed screw and open it while operating the hand lift pump or cranking the engine according to what's fitted. Remember to close the screw afterwards.
Reply to
Guy King

It won't start if you don't

If you crank it fast enough it might but it's easier to bleed the lines

Do all of them for a few seconds until there's some fuel coming out then do one at a time.

They'll let go soon anyway if they're that bad. & then you're just waiting for an engine fire. New pipes are cheap if they snap, any diesel specialist will make them up for you

That makes it easier to bleed

No

It also pumps the fuel, if there's air in there then you can't prime the pump

Take them off & hook them across the battery, if they work they'll glow

Fairly. Stick a meter on the starter, you should see over 10V when cranking. Jump leads always help to prime & bleed the system, ether start aid helps if you can't get a jump.

Reply to
Duncanwood

I have been learning a great deal from everyone. I really appreciate all the responses I've gotten to my long winded questions. I've been trying to understand as much about this system as I can so that we may successfully (hopefully) troubleshoot it, and have a working plow truck this Winter. I have been likening this injector pump which apparently is cam operated to a distributor that distributes fuel to each cylinder at, (and i'm guessing here, the bottom of the compression stroke?). Is this a fair analogy? Also when I turn the key on, if my wait light is coming on for the 9 seconds and I have 12V present at the plugs during that time then I'm assuming that the controller is working ok then? My son had added the part in the original post that he felt the plug circuit was working off the breaker but I was not sure what he meant by that. If it was would it just heat the plugs until the overload popped the breaker? If so how long would it allow the plugs to run? I guess what I'm getting at here is that I would want to be certain that the controller is in fact working. How would I determine that the controller is knocking off the plug power and that it isn't being knocked off by the circuit breaker tripping instead?

Reply to
captainvideo462002

just time it, it should run for up to about 40 seconds then cut off.

the injection pump pushes fuel in at very high pressure immediately before tdc

mrcheerful

Reply to
mrcheerful

The message from snipped-for-privacy@yahoo.com contains these words:

No, just before the top when the air is good and hot 'cos of the compression.

For an overview on how diesel engines and their fuel systems work, try here...

formatting link
Reading that will save you a lot of time typing out questions!

Reply to
Guy King

We worked on the truck over the weekend. I found that the last owner of the truck, (The state of New hampshire) replaced all the glow plug wire terminals with poorly crimped on ones. Most of these were badly rotted and loose. We replaced four glow plugs and I soldered new terminals to those wires. The plugs on the other side of the engine didn't look as bad as the ones I replaced so we left them for the time being. One battery wire was burned and loose in its connector. We cut off the connector. tinned the battery wire with good solder and installed a replacement connector. One glow plug though, the one closest to the firewall on the passenger side had a broken terminal and was so badly rusted that we could not get a wrench on it so we had to forgoe replacing it for the time being. We also replaced the batteries with two Optima dry cells which have a CCC of 1000A. and without bleeding the lines I wasn't expecting much. I put a voltmeter on the batteries and read 12.6V. We turned on the key and that dropped to 11.5V indicating that the glow plugs were on. The wait light went out after about 10 seconds but the voltmeter stayed at 11.5 V. This was puzzling but we cranked the engine and noted that the battery voltage dropped to

10.2V, (a far cry from the 8.4 V the other batteries read while cranking), and although cranking seemed slow, lo and behold the truck started! It sputtered a bit at first but soon began to run very well. After about almost a minute there was a loud "clunk" sort of sound the the battery voltage came up to about 12.2V indicating that perhaps the glow plug circuit was off. I will put a meter right on the plugs next time to confirm this but there seems to be something not right with that whole scenario. It would seem that the excessive battery load should have dropped after the glow plug timing period of nine seconds shouldn't it? The other more obvious problem is that at 12.2V running voltage the batteries do not seem to be charging. I'll have to look into that too. This truck was apparently modified from 24V I'm told. The alternator has a bat terminal a single small guage wire connected to a single terminal; and a two wire connector also. Does this alternator sound like a common one? Does anyone know where I might find a schematic diagram of the charging circuit used with this? I'm an electronics technician so I'm not too concerned with troubleshooting electrical problems if I can find suitable documentation. There is however one other issue ( besides the brake line that popped when we finally moved the truck). There is engine oil slowly leaking out from an area around the upper rear passenger side.of the engine. We thought that it was one of the engine oil cooler lines at first. I got underneath and you can see the two enginge oil cooler lines and they do not have fresh oil on them but its crowded up in there so its hard to tell. It does not seem to be one of the lines. It seems to be coming from the top left side of the engine. I'm wondering if perhaps from sitting for 7 months could it be that the very back area of a valve cover gasket just dried up? What else up in that area would ooze oil out and down that back left side of the engine and drip on the exhaust pipe? I can't imagine that it could be a cracked block but if it is a valve cover gasket it looks very difficult to get at. I wonder if running the truck up to operating temperature may soften up the gasket, that is if this is whats happening and somewhat seal this leak up. We never had a leak there.before. Any further thoughts on this saga especially the leak would be most sincerely appreciated. Lenny Stein.
Reply to
captainvideo462002

The message from snipped-for-privacy@yahoo.com contains these words:

Most diesels continue to run the plugs for a while after the engine starts.

Reply to
Guy King

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.