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Discussion Starter #1
Injection Pulse Width Error (Time Long) dtc 36
wastegate solenoid fault dtc 78

just for shts and giggles i thought i,d check for codes ,. these two came up,. and i thought/think? it runs well,.
i have never driven a 6.5 turbo before, so i,m not sure really what to expect for performance,. The dtc 78 code has had lots of reviews and advice on what to check and why,. but the dtc 36? why what who where
and when? is this a prelude to something else catastrophic about to manifest itself,.
I did just recently buy this truck, from a used car dealer in boston,. thru flea bay,.(please don't snicker too loudly).
i have an old freightliner i use for parts, it has a boost guage, so i will pirate it and install it,(after reading where to find a place to put the fitting,) the ses light came on twice so far, and both times it was under full bore acceleration, up a hill.
So far,. i love this big truck,.....
nick
 

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If the SES light is off then clear the codes and see if they come back.
 

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best place to install the boost gauge is in the upper manifold. Take it off, tap it, install fitting, reinstall manifold.

Are you getting a lot of black smoke under full throttle? If so, that 78 is giving you a hint to the problem. Its either to green dot solenoid on the drivers side of the intake, the vacuum pump is bad, or the vacuum lines are leaking. Check for at least 17 inches of mercury (negative psi) on the vacuum pump at idle.
 

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36 long pulse can indicate that the fuel solenoid is wearing. IP replacement is looming on the horizon maybe. Try adding some fuel additives to improve lubricity (2 stroke oil or Stanadyne additive, Marvels, etc) See if the 36 stays.
 

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Hey "Big Joe," welcome to the forum - love your username....:welcome2:

I agree with knkreb, that 36 might be the death knell for your IP. My last 35/36 codes were solved with a remote FSD; but with 90K+ miles on the pump, I am not counting on it lasting....I am pretty sure it is the 36 not the 35 that means the end is near....
 

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36 can also be low batteries and poor ground\power connections, causing low supply voltage to the FSD\FS - lower the voltage, longer the pw.
 

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Discussion Starter #7
thanks for the welcome minisub,.
i'll clear the codes first dave and then see what comes back, thanks for the info scruffy, i'll also remove the webbing from the upper plenum too at the same time,.knkreb i,m using an additive now,. its kleen flo?,..
GMCTD you have given me some hope, because its a used truck,. who knows if it was started with low batteries etc,..
we shall see,. i'll check for codes next time i drive it,. i,m working plenty of hours these days so it'll sit for a bit,.
Thanks for the replies it's great to be here with this truck,.
nick.
 

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yeah, unbolt and clean both ends of all the cables touching the battery, even if it doesnt look dirty hit it till you get shiny copper
 

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If your over boosting with a manual boost controller then you can expect to see the 78. The computer thinks it's still in control and starts to panic when it sees it going higher than it's told too.
 

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Discussion Starter #10
DavidPhillips;1558455; said:
If your over boosting with a manual boost controller then you can expect to see the 78. The computer thinks it's still in control and starts to panic when it sees it going higher than it's told too.
ah, good to know dave, thanks!,. the truck is bone stock,. so it will be interesting to see what the boost is (or isn't) no black smoke tho ,..
nick
 

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It would appear you have good boost with no black smoke on hard acceleration. A vacuum gauge is a good thing to have for these trucks so you will know exactly where to look next.
 

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Discussion Starter #12
update jan 31

so i did some rudimentary investigating today,..
dtc 78 is caused by (drum roll) no vacuum,..(*sigh*)
so i thought/think it runs well, i,ve a chance to put a gm8 turbo on it, so i,d guess i need a manual controller, yet theres no black smoke under hard acceleratin, (foot,. almost? to the floor) so i,m looking forward to seeing what it performs like with boost. I did have an old 82 suburban 4wd 6.2 yrs ago,. and the duallie seems like it has about the same performance which i figured was due to the extra weight,.
I also drove another guys 2000 5 spd 3/4 ton pickup 6.5, and its a complete dog,.(ses light is on steady) but i did notice that he and i have the same 215-85-16 tires, but his rpm at 100kph (62mph) is a full 500 rpm less than mine,.(his 1800, mine 2350) any way i do the math, i come up with 4.56's or 4.88's, for mine,.
nick
 

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Have your bud sign on here - he's in Limp Mode with the SES hung on

DTC78 isn't 'no vacuum' - it's high Boost, meaning the Wastegate doesn't open on demand.

No vacuum is black smoke, no power, no Boost - never gives a DTC unless you also have EGR, which you won't, with no vacuum.

Have EGR, that is..............
 

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Discussion Starter #14
gmctd;1563034; said:
Have your bud sign on here - he's in Limp Mode with the SES hung on

DTC78 isn't 'no vacuum' - it's high Boost, meaning the Wastegate doesn't open on demand.

...........
Oh,....... um,.. well,..
'K back to the drawing board,.

as for my pal his is a 2000, he has 8?? trucks with 6.5's and he's computer illiterate,. and i,m the lucky soul he's put under pressure to help with some of the related problems,. so far i,ve figured out that his 92 no start hot is likely due to a bad pump,. his lift pump doesn't work on his 97,.but i need a code reader for the 2000 and his other obd2 trucks,. i,m a dangerous man with a lot of information i half understand,.:D
but i,m tryin'!!
My wastegate arm can be moved at idle, there is no vacuum anywhere,
i will clear the codes today and then check properly my ses light,.(i,m sorry i posted before clearing the codes, ma dang) now i,m curious as to why no black smoke, (or mebbe i just can't see it behind those fat dually fenders,.
updates later, thanks eh??
nick
 

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Good.

Check the Stanadyne label on the '92 -

black label, first issue = known hot-start problems

black label, green tag, later issue = hot-start upgrades, may be worn out again

blue label, green tag, much later issue= ditto

blue label, no green tag, much much later = still ditto

Hi-mileage gonna need replacement DB2, injectors, timing chainset to restore driveability - same on any hi-miles truck, NOBD, OBD1, OBD2

DTC78 can be caused by defective MAP sensor, but not often - mebbe your vac pump puts out at higher rpm

25"hg at idle and any rpm up - 15" idle at wastegate

Harborfreight has the Cobra OBD2 reader for 40bucks, on sale rite now, usually 70bucks

With a stable fulla OBD2 trucks, yer bud should spring for a 300buck OBD2 pc scanware package - be well worth his while to get all those trucks up and running like they oughtta.

CarCode, Autoenginuity, wester's got something in Canada, maybe kennedy - search the 'net, put a burr in his saddle.

Nah, that just hurts the horsie - put a bee in his bonnet

You just need a good Win98\XP laptop with serial port and\or USB port(s), the pcware and appropriate ALDL cable
 
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