K5 troubles

[sunk]

So I have had some intermittant probems with the truck recently (89' K5 350 TBI). I got a new job (with the State) and have been commuting to Golden. It takes about a half an hour. The morning drive is un-eventful, the drive home is when I have troubles. About the end of the commute, (about a half hour in) the truck will die, roll to a stop, then fire back up when cranked (usually on Sante fe around dartmouth, crusing 50mph after lifting off of the gas [A vaccum problem right? Not that I can tell, wouldnt a vaccum problem make the truck run like crap all of the time?]) The other day, same problem, but would start, run like crap, go 10ft then die. Several times till just would not turn over any more. Had to call in a favor to get pulled home (not far). I tried replacing the fuel filter when it was cold and the truck would still not fire up (start with the easy stuff first).

I have been having problems with the starter (before these issues) and last week when the weather was warm, I replaced the starter. I also cleaned up the cap and roater (sp?) the truck fired right up. I was hoping it would not so I could figure out what was going on.

I guess I have to drive it till it breaks down again, then try to figure out what is wrong while on the side of the road. Any thoughts?

[Rick]

my friends wifes truck was doing the same thing though not a chevy(2002 dodge dakota) ended up being a cam sensor and crank sensor.not sure if you have those but thought I would throw that out there for ya.

[Jim]

Next time pull a plug wire to see if you're getting spark?

You should be able to pull the air filter and see if fuel is being sprayed into the throat.

Hmmm - I'd think yours might be an OBDI vehicle - any trouble codes?

[sunk]

OBD 1 correct, I only get a trouble code when the vehicle dies, and it clears when you cycle the ign. I ve pretty much narrowed it down to the coil or the fuel pump. Problem is that it is intermittent, and I will have to check spark and fuel while broke down on the side of the road...

No crank sensor or cam sensor (they are used in electronic ign)

Someone also told me to check the knock sensor (only used to advance timing)

I have also experienced the ign module go out. It was not intermittent.

A vacuum problem would make the truck run like crap (I am not ruling that out just yet...)

[Robert B]

vac problem would not affect much really.....at least if its stil real close to my setup .......unless you have maybe dead zero vacuum but i would thing to look at the fuel pump just cause ......... you probably have more sensors than i do so you might have one that wil affect that.......you oil sensor works correct ?? cause if it sees no oil pressure it should kill the motor a lot of times so if it (or the wire) is going bad that might do it ........should be right on top of the oil filter if its still the same as mine

[Robert B]

plus ANY vacuum leak will throw the check engine light

[xaza]

Also another easier one is to swap the fuel pump relay. Relays are notorious for having intermittent issues before failing completely. I 2nd the knock sensor, my Jeep was doing exactly same thing when the knock sensor was the culprit.

[Chris]

sunk previously posted:

[Patrolman]

I am going to place my bets on the pump. Try tapping on the tank with a hammer a bit. See if that knocks some sense into the pump (I assume it is internal). I wonder if the bad concrete expansion gaps there on Santa Fe bounce it just enough to screw it up. If the tapping helps, the pump would be the next thing I would look at. As stated, check for spark too.

[Hypoid]

I've had an intake leak and weak fuel pump (on different vehicles) cause the same symptoms.

The intake leak was an '88 Pontiac with a 2.9 liter. The heads and intake manifold were aluminum. As the engine warmed up, the leak got too big for the EFI to adapt. Once it cooled, the injectors could dump enough gas to keep the engine running. It never set a light, never set a code. When we had a scanner on it, checking real time stats, we didn't even see any dramatic change as the thing died. The final determination was made with a vacuum gauge, hooked to manifold vacuum, while we cranked the engine. Throttle closed + no vacuum while cranking = one huge leak.

The other vehicle is an '04 F-250. The fuel pump could supply the engine while it was cold. After 30 minutes of running, it could not supply the demand for fuel. Unlike the vacuum leak, the engine would restart and idle if you waited a few seconds. Again, no light, no code. The shop that we use, had to get it warmed up enough for the fuel pressure to drop.

Take some gauges with you. When it craps again, get some real numbers for fuel and vacuum.

[sunk]

Patrolman previously posted:

[Hypoid]

sunk previously posted:

[Popsgarage]

Try one of these this time. Much better pump. And, yes, my bet is the pump. Module is usually not intermittent.

http://www.highflowfuel.com/i-478356...1987-1991.html

http://www.autoperformanceengineerin...s.html#gm_apps

The High Flow Performance has a one year warranty. The Walbro pump number is FPG002. And the throttle body can handle the 255 liter an hour pump since it's a simple in to regulator, out to return system.

[Clickpopboom]

My suspect is the ignition control module. They tend to start to fail when they get hot- typically from degraded heat-transfer compound.

[88Toy]

Has the supply fuel line been rerouted, possibly too close to a source of heat? It sounds like vapor lock.

[southpaws3]

had the same problem went to a elderbrock fuel pump then check the wiring from pump to fire wall, good to go now

[gm4x4lover]

My vote would be fuel pump as well. I think I have done a fuel pump in every gm truck i have ever owned. An ignition modual wouldnt be so random, It should work or not not bounce back and forth.

[sunk]

So, it only took weeks and weeks, but i fixed it.

After replacing the fuel filter, fuel pump, fuel pump relay, and ign coil, I replaced the ign module. Turns out that the fuel injectors are controlled thru the ign module. The ign module was intermittent and every it time is messed up the ECM shut everything down, so it seemed like I was out of fuel.

I thru in a new air filter for good measure. My old K&N could not handle any more, Ive had it for 10 years.

Im back on the road, I just need to get new tires, fix my steering, build boat sides, install the 1 tons, build a roll cage, maybe a doubler, and I might be ready for the summer.....

[Jim]

Thx for the update. I always appreciate knowing the solution.

Glad to hear it's running... mostly!

[Clickpopboom]

sunk previously posted: