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

[Dieselfume1]

Thanks Thomas,

I replaced all thefuel lines this spring, and didn't change anything. if it is indeed a fuel problem, then I might just junk that filter base. 35 bucks a filter is too much anyway.

[john8662]

The glow plug controller itself controls the duration of glow, the computer in your 1991 only controls whether to allow the controller to start it's process (inhibit function only).

Unfortunately, there isn't really a way to change the controller externally for glow duration. There were some things that could be done internally, but this will take some digging to find.

So, I watched your video. That's a very poor start.

You're getting great cranking speed, so your starter and batteries are working well.

The glow duration seems a little short if that was indeed the first glow you gave it (looked like it was). I'd suggest replacing the glow plug controller. The timings are all internal, it also senses temperature, so it could be malfunctioning from that perspective.

With your start I see three potential problems:

1) Short Glow Duration and poorly performing plugs
2) Air in fuel system, drainback
3) Possible High Pressure Cold Advance/Fast Idle inoperative

Fix for number one, replace controller and verify plugs. I strongly recommend the Kennedy Quick Heat plugs, these work extremely well with stock glow times. Night and Day difference in starting performance.

Fix for number two, find a way to pressurize the fuel system from the tank on and look for weeping line connections. Use your eyes and nose to find the leak. Also possible bad fuel tank cap allowing the generation of too much vacuum in the tank which will cause a drainback condition. Replace the fuel cap with a new Diesel Fuel Only cap.

Fix for number three, test HPCA/Fast Idle circuit. Bone cold, turn on the ignition and don't start the engine. Take a 12v test light and test the power lead on both the fast idle solenoid on the injection pump and the HPCA connector on the injection pump for power. If no voltage, the HPCA/Fast idle switch (located on the passenger's cylinder head, rear behind cylinder #8) has failed, and you need a replacement.

[Dieselfume1]

Hey John

Yep, that was the first start of the day. glow time initially is about 6 seconds. I have brand new kennedy quick heats installed in the unit, and I noticed no change in the starting. (all the old glows worked)

I ordered a new filter base today (spin on) since I've already replaced all the rubber fuel lines on it. I'll try a new fuel cap too.

I'll check the cold advance also. I take it the smaller wire on top of the IP is the one that controls the cold advance? not the red power wire?

Thanks,

DF

[john8662]

Hey John

I'll check the cold advance also. I take it the smaller wire on top of the IP is the one that controls the cold advance? not the red power wire?

Yep, small wire, top cover.

I wouldn't jump to replacing the fuel filter housing, just yet. For testing, sure.

[joeq]

Hello DF, Looks like you've got some miles out of this thread. Nice looking Burb. I'll have to admit, I haven't read all the responses, but was curious about your cold start problem. I'm sure there's a lot of good advice being thrown at you, and if I could, I'ld like to contribute, if you don't mind.
I just watched your video, and noticed you didn't give the glow plugs much time to cycle. Plus you were cranking, while they were cycling. My 6.2 doesn't ever start on 1st cranks, when it's cold out. When my controller "used to" work, years ago, I found it better to wait for it to cycle on and off, a few times, B4 cranking. And the amount of time that you kept cranking your motor, trying to lite it off, was a little excessive. It really works that starter doing that. It doesn't take very long, to heat up your cables. Go out and feel them sometime, while someone else is cranking. Not sure if you've read your manual for cold cranking, or what your method is, but it says to floor it at 1st to get the fuel into it.
The most successful starting procedure I've learned on my truck over these past 22 years is this. Not sure if you'll be as successful, because my system is a little different. I've by-passed my controller, (due to cost reasons), and have it connected to a spring loaded switch on the dash. So I'm able to apply it a little differently than the controller does. also, this is when the OAT is less than 50* or so, and no block heater.
Key on, push glow plugs on for 5 sec., release for 5, and push on again for 5 seconds, then release. Immediately floor the throttle, and crank for less than 10 seconds. It may burp, but usually won't start.
2nd attempt- cycle glow plugs again twice, at 5 second intervals, and this time, when cranking, don't give it any fuel. Sometimes it'll light off, if not pump the throttle lightly, and see if it starts. 90% of the time, it will start.
If not, cycle the plugs, 1 more time, then it'll start.
It sounds tedious and time consuming, but sitting there grinding on the starter till it starts is awful on your starter. And of course, if you plug in your block heater, it'll start like it's 70* outside, even tho it's 30*.
So in your situation, don't know if you've tried this, but let your plugs cycle a few times, till they basically stop, then crank it with a full throttle. If no dice, try it one more time, and hopefully it'll go. If nothing else, please be kind to your starter. They are in a very cruel environment with these 6.2s.
If you abuse it, it will end up looking like this.

[Dieselfume1]

Thanks Joe,

I'll try letting it cycle and see if it helps.

When I start it I flat foot the accelerator pedal like the starting instructions above the visor indicate.

All the years we had 6.5s it always seemed like they fired best if you fired the immediatly after the first long glow went off. but I was pretty young then and I don't really know if we tried it the way you suggested.

As for the long cranking. I generally don't stick with it that long because I know how hot it gets the starter. It wouldn't bother me to let it try to fire off the first time, stop cranking, re-glow it, and try again except that the factory controller only comes on for about 1 second after the initial glows.

Today I picked up a new racor fuel filter base/5 micron filter. I also got a new fuel cap, and a momentary glow plug switch. We'll try them out and see what happens.

Thanks for putting your 2 cents in, I'm always open to advice especially from folks who've been able to get along with these beasts for so long!

DF

[Dieselfume1]

tried letting it cycle continually before starting, and it didn't start any better. maybe even worse.

Tonight I put on a new fuel filter base w/5 micron fuel filter included from racor through car quest. total cost $80.

got it fired up and took it for a drive. seemed for some reason like it had more power, but it could've just been the change in the weather.

we've got a blast of arctic air coming in tonight and is gonna stick around for about 7 days. I'll know tomorrow whether or not the fuel filter base was the culprit in all this.

if nothing changes, I'm going to put in the glow override switch next and see what happens.

[Dieselfume1]

ok, have tried thew new fuel cap, new filter base and tried starting last night at 10 degrees. no fire. plugged it in for 2 hours, fired up fairly well. still took a couple shots of the glow plugs before it'd stay running. If I have time I'm going to wire up the glow controller's manual override button and see how it goes. gonna be below zero tonight. we'll see how it goes.

[john8662]

Was the HPCA working?

Any smell of Diesel, or wet throttle shaft on the injection pump itself?

Did you install a piece of 1/4" clear line on the injection pump? hint: you won't find fuel rated line, just any clear tubing at the hardware store will work.

Did you install thicker head gaskets during your engine work?

Still think your glow controller is giving you too short of cycle as well, extending your glow time will certainly help if that's the case. You can glow those KD plugs for longer bursts. I've done them with 20 second glow times on my low compression engine to start.

[Dieselfume1]

Didn't remember to check the HPCA. no fuel leaks or smell of fuel

I didn't install any clear tubing. I may in the future for troubleshooting purposes, but it doesn't seem that I have a fuel problem. I have all kinds of smoke when trying to start this thing up. it's the getting fire I'm seeming to have trouble with.

I attempted to put a bypass switch in tonight for the glow plugs, but I didn't realize that the timer setup was integrated into the glow plug solenoid. doesn't appear any way to "trick it" into glowing with a manual button. Looks like a ford starter solenoid is in my future.

Might check the HPCA tomorrow.

Great to hear I can glow the kennedy quick heats longer. a friend of mine who's owned only 6.2s/6.5s all his life tells me that there was never a glow controller built for the 6.2 that was any good. they all need a manual ovverride switch for more glow time. he suggested 3 seconds on, 3 seconds off, for 3 cycles, then start.

for head gaskets, I put in victor reinz. a mistake I know. I requested fel pro's from the parts store, but they got in the victors, I was in to big of a hurry to make them send them back, plus, I figured this engine was on borrowed time as is.

[AKMark]

I went to quick heats on the 6.5 I owned and found the factory glow cycle was too short once temps dropped below 30.

I set up the factory unit to trigger an aftermarket relay, then added a momentary switch that allowed me to trigger it longer.

I would typically not use the switch until the rig didn't start on the first try. It was fun pressing the little button, after a few seconds you could hear popping sounds as the unburned fuel in the cylinders ignited as the glow plugs got hot enough.

On both of my 6.2's there's only the relay and momentary trigger. I find that typically if I count to 8, they fire right up. I typically give both rigs another couple glow shots if it's below zero just to help them stabilize. I don't know offhand what glow plugs they are running since both haven't required any maintenance in that area other than getting rid of nonfunctional factory relays.

[john8662]

Depends on which VR gasket you used. The 6.2 one is great. The 6.5 one is thicker that it should be for stock, leads to a drop in compression. Besides that's they're fine.

Thinking a compression test would be in order soon enough, that will tell the tale there.

If you find low compression (around 350 psi or lower) then you will need to look into momentary push button relay for glow times in the 15 second or so time to get dependable starts in the cold.

Besides that, injectors that are leaking will bleed down and cause hard starting as well, not real common but possible.

[Dieselfume1]

well, then I made a mistake then, I've got 6.5 VR gaskets on my 6.2

So, I'm sure I've got a compression problem.

A strange thing has happened on this machine

A few days back I ditch the oem filter base in favor of a aftermarket fuelwater seperator (5 micron). at the same time the fuel heater and water in fuel light was unhooked as well. noticed an immediate increase in power.

A couple days ago I had a day off so I decided to take the beast into town to run some errands(50 miles) To my amazement, the transmission problem I had (not shifting down from OD to 3rd at WOT ) is now fixed. If I gun it it downshifts and takes off.! Would a low power situation cause the transmission not to shift down? I re-checked the kickdown cable and it's perfect as it was before. nothing's changed there. The only thing I've done is ditch the fuel filter base. only other thing I can figure is that it's been colder than a wedge (below zero for going on 3 days strait) and that might have free'd up something that was stuck in the valve body?


Got the manual glow plug override switch in tonight and working. was super easy and cheap. I didn't plug it in tonight, and I'll try to fire it in the morning to see if using the manual glows will make a difference.

Thanks again for you help guys
!

[Dieselfume1]

Success!

Can't believe after all this time and money spent, the whole problem all along was insufficient glow time.

After dropping the fuel tank to replace fuel lines that weren't bad, replacing the filter base, replacing the lift pump and all the glow plugs, the solution ended up being a $15 relay, $10 worth of cables, a $5 switch and about 30 minutes of time.

Glow on 8 sec, off 3, on 5, ignition. bam, starts. I imagine it'll need more when the temps drop below freezing again, but usually when a diesel starts this well at 5 degress, it'll still start fine at -15

[Yukon6.2]

Right On
It seems like there might of been some restriction in the old base or filter.You should investigate a bit to see if you can find anything to confirm that.
-22 C here last night,i'm going to try to start my truck today,not plugged in so the Optimas will get a work out.
Thomas

[john8662]

Bad glow plug controller as mentioned earlier, too short of glow time.

Your 8 seconds you could have automatically with a good controller.

Low compression 6.2's and 6.5's will start well when manually glowed longer.

I think the transmission issue is too much clearance on the TV valve bore in the valve body. I spoke at length with a local trans guy about the 700. I specifically mentioned this sluggish if no kickdown out of overdrive. He said that was the issue. The only fix for it was to bore and sleeve or if not that bad drill out slightly larger a port in the separator plate to allow more fluid flow out of the relief port.

Cold outside, thicker fluid, makes up for the TV leakage.

Still worth checking on the cold advance working.

[Dieselfume1]

Well after putting some more miles on the old girl I think things are as good as their going to get.

With the manual controller it starts every time in temps of 10 degrees or above on the first try.

When it gets colder than that, usually zero or colder it doesn't matter how long I glow it, the engine doesn't have enough compression left IMO to kick over. with out glowing and cranking 4 times or so.

It was -10 the night before last, I took this video

https://www.youtube.com/watch?v=STSW8zoiR00

The video is 4-5 minutes long. and after I shut the video down, it picked up one of the weak cylinders on the RH bank. (starts loping then picks the cyl up completely followed by a minute or so of what sounds like piston slap/spark knock.)

My IP timing is about two line widths advanced. Right where the the last people that put the IP on it left it, and scribed a line. must have been done by someone with a timing meter.

The problem with the not shifting into OD at WOT came back when the warm weather came back, and I haven't had the energy to take it on. I did however install a TC lockup switch. It's been one of the best things I've done. The TC was locking and unlocking on its own, but when you put it into a stiff wind (15-30 mph) it would run unlocked all the way home (50 mi). the switch lets me lock it up and forget about it.

Mileage has been elusive. 11-14 had been average through the winter, the last couple 200 mile round trips I made driving half interstate half 2 lane of speeds between 70-80 mph, I got 17 mpg. half of that was going into a 10mph wind.

Having increased timing should help the MPG right?

I don't feel my tires are too big, but it almost acts like that.

It's got 3.73s with 31x10.50r15s on it.

someday I might have to try and drive it at 60-65 mph and see what it can do. I'm sure having a almost 300,000 mile engine with 2 weak cylinders doesn't help the mileage situation.

Am I missing anything that I can do to optimize this old girl?

I'm preparing for the worst, when this engine lets go. I've located a "known running" 83 6.2 that came out of a pickup that someone is willing to trade me for some small block chevy parts. it'd be nice to have a spare engine sitting there with fresh head gaskets ready to drop in if this one decides to scatter.

[AKMark]

My 6.2's would get about 22-24 mpg when keeping the speed below 60. My 6.5's got about 17-19, but I was going 65-70 most of those times.

The old Diesels aren't the greatest for speeds above 60.