Hello everyone. new to these forums so if im posting in the wrong spot let me know and i will move my post to the appropriate section.

I have a 1998 chevy K1500 5.0 engine, fuel injected 4x4 pickup that will not start. im getting spark and it has a brand new fuel tank, pump and filter.

I thought i had run it out of fuel one day. took me a long time to get it to fire even after i put 5 gallons of gas in the truck, it would turn and muffle a little bit then it would die. finally i got it to fire up it sounded fine at first. I got about a mile down the road and she had no power at all, if i feathered the gas pedal lightly is would go, if i stepped on it the truck would stall. i thought maybe water in the lines so tossed some fuel antifreeze in it and let it idle for a few minutes (it idled just fine ) went to go and it was still lacking power. when i gave it too much gas it made a extremely loud "backfire" type of noise but the noise was coming from under the hood and not the tailpipe so im not sure if it was actually a backfire or some sort of engine knock. now it will not start at all. i was thinking maybe i fried the plugs trying to get it to start the first time by adding fuel directly to the intake manifold (i know not recomended but it has worked in the past when the truck wouldnt start)

i have since replaced the fuel filter, tank and pump. still need to get the spark plugs replaced but i figured i would hop on these boards and see what you guys have to say.

thanks in advance for any help and if theres any info i left out please ask and ill be happy to provide it. the truck has 234k miles but has always ran well. also it is a manual transmision 5 speed

All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.



Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.


2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.


3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.










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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

the truck definatly has spak so we can rule that out.

ill have to look into tool rental to test the fuel injectors and fuel pressure.

could fouled spark plugs cause a no start situation even tho they are technically getting spark?

also what would be your first thought on the loud "backfire" type noise coming from under the hood? lack of fuel cause these symptoms, bad timing maybe? i was able to put at about 15-20 mph in first gear to get the truck to a safe location but would not get any faster without stalling.

thanks again for the help.


(This post was edited by MattMan on Feb 22, 2012, 12:34 PM)

At 234K this is open book. You may even have spark and fuel but valve timing could be off now that you said backfire and valve timing would show up with a compression check at HT suggested among the item needed for an engine to run,

T
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Tom - "Be yourself. There are enough 'other' people"

ok great, i have a good place to strat now.

when i get a compression tester ill post my results here. is valve timing something that is fixable by the backyard mechanic or is this something ill probally have to bring into the shop?

Valve timing is controlled by the timing chain which is one step more behind the water pump. It may have jumped and you'll find low compression if so and would take more than one tooth off to not run.

We hear about the timing belts all the time but even the real chains can wear out too far about like a loose bicycle chain that won't stay on the gears properly.

I would never do a water pump on a good old Chev or other like that style without doing a chain too with higher miles. All labor as parts are pretty cheap. In fact if you determine that just put on a new water pump too while there as it's off anyway.

Hardest part is getting the fan clutch off if like the ones used on trucks of the vintage still as they screw on and don't like to "unscrew" if you will

T
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Tom - "Be yourself. There are enough 'other' people"

Thanks you for your replies. im going to give autozone a call and see if they rent these tools and what the cost is going to be to rent them.


ill post my findings.

thanks again for the replies.

matt

Never rented tools but from what I know they would likely have what you need. Most will be if this is it, common wrenches and sockets a gasket scraper that could be improvised. A compression tester shouldn't be expensive if you did need to buy that...........

T
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Tom - "Be yourself. There are enough 'other' people"

If your compression checks good, check out the crank sensor. See if it has a signal coming out of it. There is a TSB out for engine kick back and broken starters because the crank sensor is over advancing the ignition. If it backfires out the intake hard enough, it can blow the gasket out the back of the upper intake creating a massive vacuum leak.













Since we volunteer our time and knowledge, we ask for you to please follow up on your threads when a problem is resolved.

(This post was edited by Discretesignals on Feb 23, 2012, 7:12 PM)

Hold off on the tool purchases and such just yet. HT has an excellent post for this at the beginning. You know you have spark, but that doesn't mean your spark is strong enough. It needs to be tested with a calibrated spark tester. You know you have fuel pressure, but that doesn't mean you have enough fuel pressure. What is the exact reading? Perhaps you have done these tests and not yet posted the results, but operating under assumptions without data to back them up can make your work take much longer and become much more expensive. The cheapest fix is the one verified to be at fault. DS also has a point with the TSB info, and worth looking into certainly. But lets see what the fuel pressure and spark quality come out to first. There may be other things at work contributing to your fault but if those two aren't right nothing else you do will make this truck work right. At your mileage level, anything could be at fault here.

Hey guys, ended up taking it into the shop for repairs and it was the spider fuel injection was all the way open and it was insta flooding the motor.

I appreciate everyones input and time and the great sugestions you gave.

now onto my next issue, a knock in the bell housing...grr. will post this issue in the appropriate sub forum though