Buying a 91 6.2 suburban that's been garaged for 5 years,any advice?

[john8662]

Shoot.

Your next task is going to be finding another set of cylinder heads.

You can go a couple ways with this engine. Being this is a 1991 verify that the casting number on the heads ends in -567. If so your head options are easy. You can replace them with 6.5TD cylinder heads. The only difference will be the precup diameter (larger). Which will still be fine, will lose just a bit of mileage.

I'd clean this engine up with some different heads and run it for as long as it'll let you and in the mean time be looking for a replacement engine.

J

[Dvldog8793]

Not good...
Your post lists "somewhere up north" If you are in Northern MN I can maybe help with the engine parts. I live next door to a salvage yard that has more than a few 6.5.

[Dieselfume1]

Checked the bad head, it's a 567 head.

Got ahold of a friend of mine, he's got a good used 6.5 head on his workbench that he told me to come and get. mentioned I'd need to use my injectors though.... I don't plan on replacing the other head, but I think it may be wise to put a head gasket in it while everything's apart.

I may put the 6.5 head on the bank that's ok if it's a lower compression head... odds are the other bank that had the bad head has two cylinders now that are going to be short on compression.

Guess I could deck the head .010 on that side LOL

Are the 6.5 heads larger CC chambers?


Also if anyone has them I'd love to have the head bolt/ intake/ and injector torque values...

Thanks so much for the advice so far!

DF

[john8662]

If the head you're getting hasn't been milled, swap the precups from your bad head into the 6.5 head and you'll be set. If it has been milled, game over for the precups. Most shops mill the heads with the cups in the head (a no-no). They are supposed to protrude from the deck .001" - .003".

Everything else should be the same.

Pick up the Hayes Diesel manual, has the torque specs for these engines. Specs are also available for paid members in the members section.

New head bolts will have the torque specs and sequence. (20ft lbs., 50ft lbs. then 90 degrees) Replacing the head bolts is necessary.

You can also use the cheaper 6.5 head gaskets with your 567 heads, the 6.5 gasket is actually better (speaking Felpro here) If you wind up with Victor Reinz gaskets you'll be lowering your compression as they're NOT stock thickness.

J

[Dieselfume1]

got her started up tonight.

ended up pulling the drivers side head to inspect for peace of mind, and found that side had already been replaced with a 6.5 head. so, I put the 6.5 head I aquired on the bad side, and threw it back together. started up and runs good it seems, although at idle I'm noticing some white haze coming out the drivers side bank... don't know what that means exactly.

time will tell if the two bad cylinders I cleaned up will hold up or not. if I bring the engine just off of idle I can feel a slight miss, so we'll have to see how that progresses.

I'll finish buttoning her up tomorrow and take it for a test run.!

[Dieselfume1]

Started it up this morning again and found that I must have had a little air in the lines yet. once it bled off the thing ran great... I still have a little smoke, out both banks, but it's very light and I think only noticeable because it's in my shop running. No bubbles or compression in the cooling system either.

after it ran about 20 minutes while I did some chores, I cam back and did a cyl cutout test on every hole to make sure there wasn't anything missing. every hole was firing.

I did the test with the advance lever on the pump to see if it was too advanced or not, and when I push the plunger in the engine gets a little more of an aggressive rattle to it. maybe it's advanced too far?

The throttle response of these engines is amazing to me.

[john8662]

Good to hear you got it buttoned up. Great amount of work in that project.

Will take awhile for everything to set in. At least it's a runner now and you can start planning on a replacement engine for down the road. But it will likely last that way quite a while.

J

[Dieselfume1]

Hey again guys, the engine's running good on this old burb, but a couple questions-

Sometimes when I go to start it hot the glow plugs wouldn't cycle. however it still started, just cranked longer. so, I bypassed what I thought was the "inhibit" switch? it's the one behind the ex manifold on the passenger side head.

Things had been working fine until yesterday morning. it was 25 degrees and I went to get the old girl started. I cranked and cranked and it smoked and smoked and wanted to fire, but acted as if it wasn't getting the glow plugs, even though the light was cycling... finally it did start, but I'm wondering, did I bypass the wrong switch?

Thanks!

DF

[DmaxMaverick]

On a warm engine, or when the weather is hot, it won't always cycle the GP's. That's normal. It shouldn't have to crank longer, however. Rather than "bypassing" the inhibit sender, you should install a GP override switch, which will allow you to glow at any time.

The reason for the hard start when cold sounds like lack of heat, likely not enough glow heat, or a too short cycle. If you're using AC60 plugs, this is expected. Either extend the glow cycle, or install an override switch to manually add glow time. Quick heat plugs do well, and don't require an extended glow time.

[Dieselfume1]

I've got the kennedy quick heats... which I'm betting are just 6v glow plugs.

[DmaxMaverick]

Most all civilian plugs are 6V. 12V plugs don't get near hot enough.

Kennedy QH plugs are about as good as they get, when it comes to getting very hot, very quick. You may have an issue with retarded timing, or the HPCA isn't working (you may have disabled it by bypassing the sender).

[john8662]

Hey again guys, the engine's running good on this old burb, but a couple questions-

Sometimes when I go to start it hot the glow plugs wouldn't cycle. however it still started, just cranked longer. so, I bypassed what I thought was the "inhibit" switch? it's the one behind the ex manifold on the passenger side head.

This switch is the Fast Idle and High Pressure Timing Advance switch. When closed gives you timing advance in the pump and energizes the fast idle solenoid.

You want this working.

If it's not starting well w/o the glow plugs check your cranking speed, possible dragging starter or weak batteries, it needs to crank fast w/o the glows working.

On the 1991 the glow plugs are inhibited/controlled by the computer. There is an additional relay next to the driver's side fender. This relay inhibits a pin on the glow plug controller keeping the controller from turning on. The PCM makes this determination based on the coolant temp sensor located on the thermostat housing passenger's side above cylinder #2.

Other than that, the PCM is used to control EGR and Transmission Lockup via the Throttle Position Sensor on the side of the IP.

Just more info for ya there...

[Dieselfume1]

Thanks guys

This thing I'm wondering now if it's a fuel issue.

thanks to you guys I found out the switch I had unhooked was the switch for the cold timing/throttle advance. hooked that back up. Tried to start it today at 40 degrees, and same blasted thing. crank and crank. white smoke out both sides till it fired.... once fired up it ran great. Took it to the shop, tested glow plugs. Glow plugs are coming on and off with the light. However, I'm not seeing that the cold advance is working. should the little plunger on the bottom of the IP be pulled in towards the pump when cold? or out? I can move it manually, but I don't think it's moving on its own.

What's strange is none of this was going on until I took it out to the shop the other night to put 2.5 inch lift blocks under the rear springs. since then I've got this cold start issue.

[john8662]

The cold advance can't be seen operating. The lever on the side of the pump controls timing advance based on throttle position and housing pressure, normal operating.

The HPCA as we call it, is a solenoid in the top cover of the injection pump. You can test this by unplugging the connector on the top of the injection pump (there are two, one is the fuel solenoid, the other the advance). Them, take a positive jumper wire and provide power to the connector, do this while it's running to if you hear the engine have more rattle (more advance).

Sounds like air in the fuel system is your problem.

Replace the rubber return line out of the injection pump with a piece of 1/4" clear hose. Observe bubbles while the engine running, also after the shuts down. If the hose drains back, you've got issues too.

J

[Dieselfume1]

picked up a check valve today to put into the fuel line between the filter base and the hard(feed) line coming from the fuel pump. Going to see if this keeps the fuel from bleeding off... I tried it to today. it fired right up, ran for 2 seconds and died out. restarted hard like it was out of fuel. I'm beginning to suspect the fuel filter base since nothing else has been disturbed except the lines going to and from the base. it's got a new filter on it too.

[john8662]

Check out the article at the top of the 6.2 forum about finding air in the fuel system.

Main point, make yourself a fuel cap with a tire valve stem in it for pressurizing the fuel tank some to find the fuel leaks.

[Dieselfume1]

Guys, just wanted to give you an update on the old girl, and to tell you all thanks again for the help getting it running

I've put on about 7,000 miles since aquiring and fixing the suburban right after I got it. It burns about a quart of oil every 700-1000 miles depending on how hard I push it. not too bad for having two holes that were pretty rough shape..

I put new tires on it, 31x10.50 r15 all terrains, lifted the rear axle 1.5 inches, and it looks good!

Everything in it works, it uses ZERO coolant.

Power is lacking, if you stick it into a 20 mph headwind it'll max out at 65.

it NEVER smokes, and I have plans to turn up the injection pump soon.

Mileage driving 70 mph averages between 14.5-17.

Starts good so far (it's summer) except for the rare occasion on a cold morning where the glows come on, and I forget or get side tracked an it starts the short cycle glows. when that happens I always have a hard start. or when the engine has been running maybe an hour prior, has cooled off enough to need the glows, but the engine is warm enough to only let the glows short cycle. those are hard starts too.

Thinking of wiring in a hot wire to a push button on the dash that is scotch locked into the harness that controls the glow control relay.

a few times this summer I had my "water in fuel light come on" I'd drain the filter, and go on, then it'd come on again 50 miles later. so I'd change the filter. so I decided to run the tank nearly empty to try and get as much water out of the fuel as I could. changed fuel filter again and haven't had a problem since.

Winter is coming on here soon so we will soon see how well the glow plug system is really working.

As for the trans, I rebuilt it myself due to a planetary failure right after I had all the engine trouble earlier in the year. it was my first time and it went pretty well! while I was there, I also discovered that the transmission was pushing fluid into the transfer case because of a bad seal. so I replaced that too. changed diff oils while I was at it

Since I had the suburban for so little time previous to this, I didn't really get a feel for the normal shift points before I tore the trans down.

Now that it's rebuilt, the tv cable is new, and adjusted properly,
the 1-2 shift hits at about 25, the 2-3 at about 38 and the 3-4 at about 52.

what really bugs me is the downshift. it won't kick down from OD to pass unless I shift it manually, or get down to about 48 mph.

Every shift is good and firm and otherwise shifts drives, and the tcc lockup works like it should. The torque converter was not new, but off of a used 94 4l60e trans (mine) that failed 30K after a rebuild from a slipping forward clutch.

it's been my experience with other 700r4s that anytime the acc pedal was flatfooted it always shifts out of OD, no matter the speed. only exception was for law enforcement vehicles. were the diesels this way too?

This sub has 3.73 gears, with 31 inch rubber. don't know what kind of effect that might play?

Maybe I'm worrying about nothing?

Thanks again for all the help guys!

[DmaxMaverick]

Sounds great! It's always nice when things just work.

Now, to clean up a few rough edges (in no particular order)....

If you're getting no black smoke at all during hard acceleration, the pump could probably use a little turn of the fuel screw. Don't get greedy unless you have an EGT gage. No more than 1/8th turn at a time.

3.73 gears and 31x10.50 rubber was OEM for many models, so nothing unusual there. Shortening the gears a bit will help with power, but it also increases the noise at highway speeds. Should be no hit to mileage, though.

The WIF lamp does more than just suggest water in the filter. It also suggests a pressure differential, usually meaning a plugged filter. The next time you drain the "water" from the filter, capture what you drain into a clear jar and cap it tightly. Let it sit for a couple hours, and see if there is actually water in it. After a long period of not running, other crud can build up (or grow) in the tank, which will eventually make its way to the filter.

An override button for the GP's should take care of your hard warm starts, and may help in the winter.

If it doesn't downshift from OD at WOT, the TV cable is not adjusted properly. Also, I'm surprised you've had success with the 4L60 converter. The ones I've seen used weren't worth the money saved. They weren't designed for the Diesel RPM range. It may have something to do with your no-downshift issue, but I'm not sure.

[Dvldog8793]

Howdy
Just a side note....Stay away from scotch locks. Take the time and do a good real splice into the line. a scotch lock basically just cuts you insulation and weakens/cuts the wire making a persfect point for "issues" in the future. I've seen more problems than I can remember caused by them in the ESV field when I worked at Motorola....
Sounds like a nice rig coming together...What pump series is it?

[Dieselfume1]

Thanks for the advice guys.

I'm not sure what series of IP it's got, It's fully mechanical, that's all I know and the pump and IP supposedly were changed right before I bought it. Didn't find out till later from a neighbor that the reason the previous owners changed it was because they accidently filled the tank with gas and drove it till it didn't want to run anymore (about 5 mi)

The 4l60e TC a friend at the trans shop told me is almost identical to the diesel unit except for it has 3 mounting pads for the flywheel instead of 6. he said there's no way that a 6.2 will ever have enough power to rip the 3 pads off of the TC. the lockup speed he told me is about 100 rpm difference. won't even be able to feel it.

I had about $250 in a transmission kit, and wasn't going to put any more into the transmission of a vehicle that was starting to look like a really deep money pit!

Wondering if I have a piece of junk in the throttling valve? the valve body was the only part I didn't tear down when I did the trans overhaul.

The tv cable I adjusted to be fully extended when the pump is at wot. only thing I'm wondering is, if I'm actually getting full throttle from the pedal in the cab? guess I need to get some help to hold it to the floor and see if it's actually getting full throttle.


I replaced all the rubber fuel lines going to and from the transfer pump, also replaced the transfer pump and put a check valve in the line after the fuel filter. none of this helped the hard start problem I was having this spring. but, since I've put a pile of miles on it this summer it's not had any hard starts to speak of that wasn't glow plug related, and I've been running a pile of power service and lucas fuel conditioner through it.

I put some oem aluminum 15 inch wheels on it and man it looks good. gets lots of looks as this "survivor" drives though town.

I've got a banks pyro I had on another vehicle, I could throw it on there, and try turning the IP up a little. My duramax has no problems at 1300 degrees, how about the 6.2s?