I have a 1988 GMC S-15 Tech 4 motor it fires but will not crank and run! I've changed plugs , plug wires, distributor, cap, rotor button ,relay&new battery! What could be the reason it won'

no,the pump wouldn't do that. Pull the dist cap and crank the engine,make sure the rotor spins,may have sheared the pin one the shaft.

well hopefully the engine is not siesed get a socket and a cheater and find the main pulley witch turns the crankshaft and see if you can crankit if you cant then chances are it locked up

the timing is off a bit! heres how I do it. remove the number 1 plug, stick a straw or similar in plug hole. turn engine over by the crank shaft with a wrench. when piston gets to very top of bore, just before it goes down. this is tdc. remove distributor cap and remove distributor reposition the distributor rotor button facing number 1 plug wire inside cap. replace cap and try it! please let me know if this works for you. good-day ! if you can not get to number 1 plug. just turn the crank to tdc marks are on damper pully or crank. is this a 5.7,

#1 plug is closest to the front. Take off distributor cap. Remove #1 plug. You want to crank engine until #1 cylinder is on compression stroke. Watch to see direction the distributor rotor is turning. As the compression stroke starts then bring the engine to top dead center by aligning timing mark on crak shaft pulley with pointer. The #1 plug wire goes in the distributor cap hole the rotor is pointing. The #2 wire in the next hole following the direction the rotor turned. Then the #4 wire and finally #3. Firing order 1-2-4-3.

Just wondering do you still have this truck? If so email me at [email protected]. Thanks!

This diagram is for 1998-1995 Chevy 6 cylinder 4.3L engines.
Your got the firing order exactly correct, at 1-6-5-4-3-2, but here's the thing to double-check:
The distributor rotation is clockwise (note badly rendered arrow in picture).





Since you probably got everything right, then you're left with really unusual/rare causes of
failure of the ignition system:
(a) rotor button misaligned/failing to make contact?
(b) rotor button not pressed onto distributor shaft far enough therefore failing to provide correct
proximity to distributor cap contacts when coil fires
(c) coil wire or contact loose/disconnected - press coil wire firmly down into distributor cap.
(d) distributor shaft of other damage caused during installation of rotor.
(e) spark plug wires defective from factory
(f) spark plugs defective from factory
(g) battery low - may need a charge to start
(h) ICM (ignition control module) failure - hook up your HEI (high energy ignition) tester, and
watch the quality of the spark on each cylinder.
(i) fuel problem? If spark is being properly delivered, its gotta be a fuel problem...
(j) distributor cap not screwed down flush to top of distributor? maybe just on one side?

Inspect the inside of the distributor cap - if there are lots of little metal bits all over the inside
of the distributor cap, then you know you have a misalignment of some type in there, and the
rotor and cap are destroying each other. normal operation will throw a quota of spark-ed off
metal bits inside the distributor cap, but since your cap is brand new, your attempts to start
the engine should have rotated the distributor so few times, you should see no metal debris.

Inspect the distributor cap contacts to see if any spark marks are more of less in the middle
of the cap's proper "contact zone". If not, you've diagnosed an internal misalignment, which
you know how to correct.

Inside or directly under the distribitor cap is a plastic ring with either one or two wires attached..... these devices fail and not allow the engine to start.
It happened on my 88 chevy (305 cu in.). a quick fix is to replace it with a new one.. (Advance Auto) or other parts store.

you said you repl dist cap that means you don't have a crank sensor you have electronic ing module. remove your elec ing module have it tested most auto parts stores could test your module, or check your coil at the neg terminal. should have power. if not you lost your primary volt from your batt.your secondary power is coming from your electronic ing module from the module to the pos terminal on the coil, when the eng cranks,from the coil to the dist cap , from the dist cap center to the rotor then out to the plugs,this all happen pervided the timing belt or timing chain is ok. the cumbustion chainber needs 3 things , thats fuel, air, and spark.

FIRING ORDERS

To avoid confusion, ALWAYS replace spark plug wires one at a time.

The most important thing to remember about the removal and installation of a distributor, cap or spark plug cable is that all wires MUST be labelled before they are disconnected. Keep in mind that these figures depict a firing order where the distributor cap terminals are relative to EACH OTHER only and they do not necessarily depict the tower positions in relation to the rest of the engine. This is true because any distributor which has been removed and reinstalled may have been installed with the No. 1 spark plug tower at any position (360 degrees) in relation to the rest of the motor, as long as the rotor aligned to the No. 1 tower when the No. 1 cylinder was at TDC of the compression stroke (valves closed, ready for the plug to fire). As long as the remaining wires were connected in the correct firing order sequence (depending on direction of distributor rotation) the engine will run. DO NOT EVER remove more than one wire from the distributor cap at a time unless you tag ALL wires and towers to assure proper installation.



Fig. 1: 1.9L engine . Firing order: 1-3-4-2 . Distributor rotation: counterclockwise



Fig. 2: 2.0L engine . Firing order: 1-3-4-2 . Distributor rotation: clockwise



Fig. 3: 2.5L engine . Firing order: 1-3-4-2 . Distributor rotation: clockwise



Fig. 4: 2.8L engine . Firing order: 1-2-3-4-5-6 . Distributor rotation: clockwise



Fig. 5: 4.3L engine. Firing order: 1-6-5-4-3-2 . Distributor rotation: clockwise

I hope help you with this (remember rated this help) Good luck.

You must have the plug leads in the wrong place on the distributor.
Firing order is 1-3-4-2
Remove the distributor cap. There is a tiny mark on the aluminum body where the cap sits on it. Turn the motor clockwise by hand until the rotor lines up with this mark. #1 plug lead should be in the distributor cap hole closest to the rotor in a clockwise direction.
If the motor still does not start rotate all the plug leads 180 Deg.