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Hard starting in cold weather with 98/95 merge

bison

bison

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Near Peace River-Alberta
Follow up on dead pedal.

I rebuild the engine and parked it in my 98 14 days ago.I used all wiring harnesses [checked toroughly] from the 98,+ all sensors including CPS and a brandnew CTS. I remote mounted the FSD and heatsink inside the pass fender intake airstream.[stays nice and cool there at all times]
The truck starts and runs fine since, been inside overnight , no trouble.

guess what? last night the truck slept outside,was 20 below. this morning it fired up instantly and had right away the same problems as stated in my first post. So the damn gremlin followed the truck. Check engine light came on once briefly and there are no codes set or present. It only appears to be doing this in subzero temps.The glow system works perfectly fine. fuel supply is exellent.
IP issuess or what? I cant think of anything else now. IP has only 15 k on it. former owner had the same problem about 10 k after new IP install, but never went back to the dealer to get it rectefyd.

Anyone?
 
This is likely a dumb question, but have you checked the timing? When it's cold, the timing changes to accommodate; it seems to me the problem is temp-dependent and only with a cold engine, so it seems to follow something isn't accommodating...
 
According to the gm manuals :any time the cps,ip ecm or engine is replaced you must do a time set and tdc offset learn. It may not have been done in the other truck either.
 
To above 2 posts.

I lack the proper scanning tool to a time set or tdc offset.the IP was left on the timing cover for that reason. I did install a new chain however. By the sound of the rattle it seems the timing is a tad early though.

The IP , when still in the other truck was dealer installed, why would the symtom apear after 10.000 km and not right away after install if time set and/or tdc offset was not done.Per former owner the IP was replaced in early winter,and started to experience said problem only in the following late fall.

Would this not set a code?
 
I'm going to throw out something else. You'd mentioned your fuel pressure at idle is 3 pounds. I prefer more like 8 or 10 at idle. I wonder if you don't have a slight air leak, that after sitting drains off just a little pressure. It starts on the fuel in the IP, then gets some air, then works it out.

Any leakage underneath?
 
Nope,fuel pressure is 6 psi at idle on this vehicle. New LP, in cab fuel gauge and OPS/ glowcontroller bypass switch are installed. IP return line is clear plastic and always full of fuel,even overnight.
when the symtom is present there is some blue and black smoke,[but not as exessive as when the engine was still in the donor truck].When the engine comes on stream,[starts to rattle evenly on all 8] all smoke disappears, and it runs happely ever after.
 
Have you tried the good trucks PMD. I see you remote mounted it so it would be easy to swap for a test??
 
re: setting the the tdc offset - that's a value remembered by the PCM, and has nothing to do with the position of the IP. Well, you know what I mean. When your IP is in, and you do a TDLearn, it sets the value in the PCM and that governs how the IP input signals are managed... if you then change (move) the IP setting without re-doing the TDLearn, the PCM remembers the old value, right?

If the engine was out, if it now has a different PCM, then it is quite likely confused.

That could very easily account for your temp-dependent issue.
 
no OS harnass,I used the 98 harnass. PMD swap dont make no diff,I tried that today.
So would Koko relearn make any diff,
Damn I need a tech-2 scanner! the one i have is a innova OBD l&ll, i cant seem to do dick all with this thing.
 
You have to do a TDCO set, takes about 5 min if you get your hands on a scanner. Do parts stores rent those out? Try unplugging the cranks sensor and see if it starts. If it wont start, start it and then unplug the sensor and see if it kills it (which it shouldnt unless PCM is using it to determine fuel flow as the backup) Supposedly it should start with the crank or optical sensor unplugged/inop but not if both are unplugged/inop, so if you unplug one it should start and if it doesnt maybe the other is bad. However, thats what my manual says, and it doesnt start at all when my crank is unplugged. Maybe its because mine is early off the line in Nov93

Did you move the filter assembly with it? Fuel Heater in the Assembly? Using same fuel type, what type of fuel? Using additives? Fuel becomes cloudy at freezing 32F and can gel at 15F clogging your filter, and the fuel heater in the assembly might be resolving your issue after a few minutes. If filter is clogged pressing pedal isnt going to help much.

If you have a digital multimeter, pull the optic sensor harness off and check the resistance (ohms) through pins E and F. Around 32F you should read 9-10K ohms, 50F 5-6K ohms. Thats your fuel temp sensor you brought with the IP. It only codes if it reads below 6F or above 215F, not if its just wrong.

Try fooling the PCM and unplugging coolant temp sensor and placing a 30Kohm resistor across the harness contacts so it thinks the coolant is at around 174F and see if it does the same thing.
 
Last edited:
My parts store rents out dick all. OS and CPS checked out good, all it got me is codes.

Now gelling of the fuel could be possible cause the tank was full and the truck had been sitting for 5 yrs since last run and could have summer diesel in it[it did'nt cross my mind altough i did chuck 1/2 a can of conditioner in it.].
But the donor truck had same problem with winterdiesel.

resistorjumping the CTS might be worth trying.I'll have to wait for a frosty night to do that.

I start thinking the advance may be sticky
 
bk95td said:
According to the gm manuals :any time the cps,ip ecm or engine is replaced you must do a time set and tdc offset learn. It may not have been done in the other truck either.
Click to expand...

You should be able to start with stored values, unless your timing with replacement IP is WAAAAY of the mark, TDC relearn would be to fine tune for performance/driveability, this is not the case here.
 
Okay lets back up and take a breather, we have a rebuilt engine, new injectors, new OPS, new lift, new Fuel filter, IP<15K on it not moved when engine rebuild (how did you manage that), new timing chain (how did you get marks lined up if you did not pull the IP), are you sure you were at TDC when you checked timing?

new PMD/FSD (new or new to you, did you put in a resistor), new CTS, filter manager is full of fuel ??? (how did you purge it)

I see no mention of glow maintenance (new glows ???, all getting hot ???, getting juice to them out of the glow controller???)

please correct any missed points
 
This vehicle is running, it starts, and has poor performance first off, so it does basically run, but there may be a timing or TDCO issue. Might not be the only issue.
 
Turbine Doc said:
Okay lets back up and take a breather, we have a rebuilt engine, new injectors, new OPS, new lift, new Fuel filter, IP<15K on it not moved when engine rebuild (how did you manage that), new timing chain (how did you get marks lined up if you did not pull the IP), are you sure you were at TDC when you checked timing?

new PMD/FSD (new or new to you, did you put in a resistor), new CTS, filter manager is full of fuel ??? (how did you purge it)

I see no mention of glow maintenance (new glows ???, all getting hot ???, getting juice to them out of the glow controller???)

please correct any missed points
Click to expand...
OK TD, IP not moved.This engine was taken down till the last bolt. I left the IP On the aluminum timing cover housing.Cause i could have marked the pump to the housing and removed it but did not see the point in doing that. Cant see what is so strange about it.
The crank and cam sprocket and chain are installed as a unit[marks facing if i remember correct,was 1/2 yr ago]add the camshaft/IP drive gear to the cam,turn the crank to get the mark on camshaft gear straight up,bolt the timing housing with the IP on, install IP gear on the marks with IP dowel in the slot,and done. In any case the timing is 100% correct on that part. The engine started up in the first try without the slightest hitch.a nice rattle from the get go.[ even i was impressed]

New nozzles set to 2200 psi within 50 psi of each other[done in house]
OPS is used but good[I got fuel gauge in the cab as well,Tee'd in between filter and IP] New LP 6 lbs at idle.
I have a clear IP fuel return line.Is full of fuel at all times,no leakback observed yet.

Brandnew PMD and yes it is also new to me:D, Resistor in from the old one{old PMD does duty on my wife's truck for a while allready}.

Fuel filter relocated to the dr side fender, purged all the way to the IP inlet with help of a OPS/extra glow bypass switch installed in the cab.
New G-60 glowers,glow circut is working as it should.

Hey TD, I 've been wrenching for 40 odd yrs. the mechanicals dont hold any secrets, The electronics on these IP's still do.

I dont know what to add here, other than the hickup in below zero innitial start up this thing runs like a charm.I put just short of 250 km on it .

The engine came from a truck i bought with this gremlin present, but trashed it in short order[I lost a argument with a semi]
 
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