Cant adjust timing.

I just found my sticker on line last night for my 75 GMC. Go to : www.gspp.com Thats Golden State Parts and they have pic's of all the decals they sale and you can get all the info you need. By the way your 250 inline 6 was used in the 75 truck also 2 bll barb, so that sticker will work for you. It has complete instructions for tune up and spec's.

Hope this helps Mike

Timing should be set by the PCM. So you cant adjust the timing. However if you have a faulty knock sensor the PCM cant tell the proper time to fire. The knock sensor picks up on ignition ping and adjust the time to send spark to the plugs.. Other causes of ping can be the engine temp, faulty EGR or the engine can be to lean.

Do compression test first. Have you got a blocked air intake? Sometimes people put a rag over the intake tube inlet when blowing outthe air box & forget it & it gets sucked in & blocks airflow. The things I think of are straight away are Spark, Fuel, Fuel pressure, Air, Timeing, Compression

Don't try to adjust the idle speed. Very very bad thing to do. Have your idle air control unit checked. Probably shot, or carbonrd up. Also have your throttle body cleaned.As far as the shifting goes, have the shifter interlock checked. These are both things that are better left to pros, as the diagnosis requires special equipment, and information.

Adjust the rear brakes by lifting the handle up and down lots of times thus tightening the brake cable.

make sure the brake light switch is mounted and adjusted properly. they have been known in older cars to actually fall out of their mounting hole which in turn makes the brake lights stay on all the time. if it all looks good then it probably needs to be replaced. most new switches are self adjusting so that helps!

Hello: Parking brakes are normally at proper if the brake shoes are properly adjusted. Any ad justment you find on the cable should not be used untill the brake shoes have been adjusted first. The cable adjustment is for taking uo strech slack as the cabble streches in time. Get a proper adjustment on all brakes first. You may not have a a secondary adjuster, Good luck.

this is the way i adjust tappets remove all spark plugs


153
-----------
624
draw this on a paper

u start with no1 get the valves rocking which means turn engine over by hand til no 1 rockers one rocker is going up and the is going down u may have to turn the engine back and forth slowly
to see it . once u have no 1 rocking u can adjust no 6 valves adjust them with a little clearance so the push rod still spins freely

next look at chart
1 rocking adjust 6
5 rocking adjust 2
3 rocking adjust 4
6 rocking adjust 1
2 rocking adjust 5
4 rocking adjust 3

once u have made these adjustments recheck firing order 153624
try and restart engine if it starts the turn all rocker ajuster a further 1/4 of a turn and your done u may have too wait a bit of time for the liffters to bleed down after u do final adjustment if it dont start

hope it helps please leave rating and if u need more help let me know

try checking the fuel filters for dirt, clean if necessary!
i don't know if this is the exact copy of the idle adjustment of your car
the idle adjustment screw is on the carburator area. nearor just below the air filter.

Hi, I think you will find that providing the crankshaft, camshaft and injection pump were properly locked when the cambelt was fitted all the fine adjustments are made by the on-board computer as you drive along. If you suspect that the timing isn't correct, get the fault codes read and post them here and I will try to help you further.

This is just my first message, so please don't "rate" it yet unless it really has fixedya :-) If necessary, "add a comment" down at the bottom and tell me what else is wrong. Thanks, D.