More Newbie Questions

[cwlehner]

Hi,

I have an '85 6.2 with a 94'ish 6.5 turbo see http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=008503 for pics. This is my second 6.2, but the turbo stuff is all new to me. When I bought the truck the owner said that he normally ran about 7 psi max boost, but a mechanic buddy of his thought that was too low and "cranked up the pump". Now it runs about 10psi under moderate accel, and 14 at WOT. I see about 7 PSI while cruising. Is this too much? Every once in a while I get a little surge while cruising at 65+ MPH and I see the boost guage jump about 3 PSI (speed jumps about 3-4 mph too), I also feel an occaisional sag and see the boost drop. In either case, it isn't that objectionable, but I know it isn't right and would like some pointers on what the cause may be.

2nd issue: It is a hard start when cold. My other 6.2 with a manual GP switch and AC 60G's would start without plugging in at 20 below. My new truck is a hard start at 40 above. The glow plugs are all new (as per the previous owner - they look new too - took most of them off cause previous owner didn't use anti-sieze). The thing cranks fast. When cranking I can hear one or two cylinders firing, I get tons of white smoke mixed with some black. When it does begin to run, it takes a few seconds for all of the other cylinders to come alive. I don't think all of my plugs are working right, but am not sure. Is there a good way to test glow plugs? Hot it starts almost instantly. When plugged in for a few hours, it starts easier, but not as easy as my other 6.2 does without plugging in...

Last issue: My "water in fuel" light comes on when I accelerate. On my last truck I would have changes the fuel filter on the firewall, but this truck doesn't have one (see pic at link above). Since I have no manual, what should I do.

Any help is greatly appreciated.

Thanks!

[jackrabbit]

I'm a bit confused, from your pictures it shows that you do have the old style 85 6.2L filter still mounted on the firewall and you already know what needed to be done (change it) when it came on under acceleration.

Am I missing something?

I can't address the first two items since I don't have any experience with this engine.

[slagona]

...normally ran about 7 psi max boost, but a mechanic buddy of his thought that was too low and "cranked up the pump". Now it runs about 10psi under moderate accel, and 14 at WOT. I see about 7 PSI while cruising. Is this too much? Turning up the pump does not necessary give you more boost - just more fuel. There is a wastegate on the turbo - that is what would be adjected to allow more boost. The original wastegates were not adjustable. From the photos, I can't tell what you have for a wastegate controller. For a non-intercooled engine, it's recommended to keep peak boost at 10-12psi max. Otherwise intake air temp gets too hot and has diminishing returns. See if your wastegate controller is adjustable (some sort of spring contraption in which you can adjust the tension on the spring).


Is there a good way to test glow plugs?To test the plugs themselves, unplug the electical connector to each plug. 1st, use a volt meter to make sure each plug is getting power when the glow plug controller cycles. 2nd, use an ammeter, going directly from the '+' battery post to the glow plug - it should draw 10-12 amps within a few seconds.

I'd do a compression test to see what shape the engine is in. There are several members in Michigan, including myself, that have compression tester that you might be able to borrow. Where are you located?


Last issue: My "water in fuel" light comes on when I accelerate. On my last truck I would have changes the fuel filter on the firewall, but this truck doesn't have one From the pictures, it looks to me like your truck is still using the stock fuel filter mounted to the firewall - between the engine and the A/C Evaporator. It is the rectangular box, held on by the two metal "clips". It's a Stanadyne 80, if I remember correctly. If that is not being used, then it was converted to the newer filter, which sits under the turbo power cover, behind the pump in the valley of the engine. It is a Cylinder shaped unit with a black plastic screw-off top.

Good luck with your new truck, still my favorite body style....

--Scott

[ 04-26-2005, 04:46 AM: Message edited by: slagona ]

[DmaxMaverick]

First of all, if you are getting the WIF light on hard acceleration, your M80 filter (square canister on the firewall) is probably still in use, either alone or with another filter. It is the OEM filter on '85, so the parts store will list it as such. WIF light on these does 2 things. Detects water in the filter, and detects pressure differential before/after the filter (indicates plugged filter). It is telling you it (the M80) needs changing, for either reason, usually pressure differential. If you do have water in the filter, it will usually stay on for longer periods.

Next, take that "turbo power" cover and toss it, sell it, or whatever, just get it out from under the hood. It does nothing but look pretty, and "blanket" the upper intake and retain heat.

Lastly, your boost pressures are too high unless you have an intercooler. Melted pistons will be forthcoming, if your head gaskets last long enough to allow it. 7-8 PSI should be max, with an ocasional peek of 10. Either turn the pump back down, or keep your foot out of it. If others drive your truck, they'll likely do it in for you, unless they know what you know. Install an EGT gage and use that as your guide with a boost gage. The '94 turbo isn't very efficient above 10 PSI and gets worse the higher you go, which translates to diminished returns above 10. Higher boost won't give you any appreciable power, just more noise, heat, and fuel consumption.

Also, which tranny does it have? OEM TH400 (3 speed), or has it been changed to a 700R4? Many of those have been upgraded, which is OK if it was done properly, but does require additional consideration.

Either way, looks like you got a nice truck. Take care of it and it will do the same for you.

[cwlehner]

First off, thanks for all of the help.

Re: Fuel Filter

With all of the wires and stuff coming out from behind it, I guess I thought it was something different (told you I was a newbie, my last chevy had the cylindrical filter). I bought a filter last night. Are there any special installation instructions??

Re: Boost

I was told the turbo and all related hardware came off of a '95 6.5, but others who have looked at my pics think it is 94 or older. From some of the replies, it looks like this makes a difference. Also, I have no idea where the wastegate is located or what to look for (but with the slight surges I get, there must be something allowing boost to increase). Pointers appreciated. Just for reference I am running about 4 PSI boost at 55mph, 5 to 8 PSI at 70 MPH, 10 PSI max on a launch (briefly), and 14 PSI at WOT during trans downshifts above 25 MPH (1-2 seconds). Is this still too much? DmaxMaverick mentioned looking at EGT. Where would I get/mount a sensor and what temps should be considered max

DmaxMaverick also asked what trans - it is orignal TH400.

Also, the last owner mentioned turning up the injector pump to get more boost, but Scott said that that just gives more fuel. Since I get a lot of white smoke at cold startup with some black mixed in should I turn the pump back?

Re: Plugs

Thanks for the test procedure. Scott mentioned that there are several members in Michigan, and there may be a potential to borrow a compression tester. I live in Howell and would like to get aquainted with some folks who live locally and know these engines well. I work for GM powertrain as an engine calibration engineer, and there seems to be a lot more expertise with the 6.2/6.5 on this website than I can find here at work.

[slagona]

Probably one of the best ways to get info from this forum is to use the search feature in the upper right hand side of each page. You can spend days learning about your engine. A lot of great info here.

> Where would I get/mount a sensor and what temps should be considered max.

You can order an EGT Guage and associate hardware from any of the suppliers here, or pretty much any auto store. Locally, I've used RamChargers to get Autometer guages. They may not have what we need in stock, but can get it in 1-2 days. For EGT, the choice is to mount it before or after the turbo. Before the turbo gives a more reliable reading (turbo takes a somewhat known amount of heat from the exhaust and therefore lowers the exhaust temp giving you a lower reading if mounted after the turbo). However, there is the small chance of the pyrometer probe breaking and taking out the turbo if mounted before the turbo. I've never heard of this happening in the 8 years I've been learning from TDP and this forum. In either case, it's easy to install in either the cross-over pipe or the downpipe if you are looking for a quick installation. Most come with a band clamp type installation option - simply drill a hole in the pipe and install the probe with a clamp. Run the wires to your guage and you're done..... Other ways to install the probe are to drill/tap the passenger's side exhaust manifold under (before) the turbo - there's a nice flat spot there, On a previous engine, I tapped the driver's side exhause manifold right at #7 piston with good results. You can also weld a bung on either pipe and install the guage....

Acceptable EGT before turbo are about 1100 *F or lower if reading before the turbo, about 100 *F more if reading after the turbo.


> Also, the last owner mentioned turning up the injector pump to get more boost...

Turning up the pump gives more fuel. More fuel can result in more boost, but more fuel is not always a good thing (you need to burn all the fuel). Adjusting the turbo in some fashion (electronicaly controlling or manually controlling) so that you get more boost with the same amount of fuel is what you really want (within limits).

> Since I get a lot of white smoke at cold startup with some black mixed in should I turn the pump back?

Turning the pump back probably will not solve all of your cold-start smoke problems. Black smoke indicates that there is too much fuel - not all of it is being consumed. Turning the pump back may eliminate the black smoke at startup - but it may not.... It probably will not help with the white smoke. White smoke could be a variety of things - timing, bad glow plug system, low compression, air in the injection system, injection pump, .... Check out the 6.2/6.5 Trouble shooting guide in the members area for more info on White/Black smoke.

I live in Lake Orion and work in Troy. I don't get out your way much, but if you're welcome to borrow my compression tester. If you're ever in my area, let me know and we can get together. Which powertrain location are you at?

[DmaxMaverick]

Acceptable EGT before turbo are about 1100 *F or lower if reading before the turbo, about 100 *F more if reading after the turbo. I'm sure you typo'd, Slagona. Post turbo temps should show 2-300

[slagona]

Yes, thank you for the correction - not what I had intended to say..... I think was was trying to say that actual temp is more than what you are reading.... but failed......

[cwlehner]

I replaced the fuel filter - no more surges, water in fuel light is gone, and the double bonus it starts ALOT easier (any ideas why?)!

Thanks to all who helped.

[DmaxMaverick]

Originally posted by cwlehner:
I replaced the fuel filter - no more surges, water in fuel light is gone, and the double bonus it starts ALOT easier (any ideas why?)!

Thanks to all who helped. The filter was plugged. It's amazing what can happen when the fuel supply is restored.

[opto]

I once had a not so old filter block fuel delivery so much that I almost lost all power and could only get it to run at 10-15 mph.

Indeed strange things happen when not fueled right