Why doesn't it fire at all?

Check your wiring to and around the dist. for burning and failures.

Assuming your truck is old enough to have a distributor cap and wires, either one could be shorting out when wet or damp.
You may need to replace the cap, rotor and wires to fix the problem.

Check out the related help links with solutions to troubleshoot the problem.
Click the link below:----
1990 Toyota 4Runner: Engine cuts off when reaches 2000 RPM?

http://whatisbyme.blogspot.in/2012/05/1990-toyota-4runner-engine-cuts-off.html

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Volvo 760 engine cuts off frequently while driving? http://schematicsdiagram.blogspot.in/2012/02/volvo-760-engine-cuts-off-frequently.html

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Car starts and cuts off immediately? http://repairhelpcenter.blogspot.com/2012/01/car-starts-and-cuts-off-immediately.html

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Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html

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While stop engine idles like cylinder missing? http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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These details will help.
Thanks.

If The code Is PO301 PO302 PO303 PO304 or any one of them .Will show miss fire, Has the car ever been tune up, If not change the (Spark) Plugs,End if that doesn,t work ,Also change the sparlk plug wires, Go the cheap route first. How many KM is on the car?

http://www.autozone.com/autozone/repairinfo/specifications/specificationsMain.jsp?childCatName=Firing+Order&childCatId=26200242&categoryNValue=26299999&categoryNameForTitle=Ignition+and+Tune+Up&categoryName=IGNITION+AND+TUNE+UP&childCategoryNameForTitle=Firing+Order

Hi i need help my mk1 golf carb starts and idle fine but as the car idle and enjin is getting hot then she just jerk and cut out then start it again it starts fine but idle for aboutfew sec then cut out again..i unplug the temp sensor problem remain petrol filter new new plugs and plug wires new boch distributor...plus 1/2 tank of feul...what els can i try any help..can this be electrical problem or what all my fuses checked and is fine any help pls

Your first problem is to find out why the intermittent no-power problem. Honestly, that sounds like a loose conmnection somewhere. check all your grounds for clean and tight conditions Also, battery connections and alternator connections. Double check your power distribution center for any loose wires or poor connections. Once you solve that problem, then you can diagnose the other problems with poor idle and temp. gauge.

IF YOU RECENTLY UNHOOKED BATTERY OR HAD DEAD BATTERY THE COMPUTER WILL NEED TO RELEARN IDLE STRATEGY,START VEHICLE KEEP IT RUNNING AND DRIVES ON 2OR 3 MILE RUN SHOULD BE SUFFICIENT IF THIS DOESN,T WORK LOOK FOR VACUUM LEAKS IN ENGINE COMPARTMENT OR POSSIBLE BAD IDLE AIR CONTROL LOCATED NEAR THROTTLE BODY

Idle set to low.
Or, idle step motor defective/dirty

ICM idle control module, loc throttle body, it may be dirty, remove clean or replace, its easy..