Help! Sometimes starts perfect, sometimes won't start at all

[ddavis]

I've got a 1999 Astro van with about 125K with a split personality. On a good day it fires up immediately and drives perfect all day. On a bad day it turns over but will never fire up. There doesn't seem to be any pattern as to what is causing a good day or bad day (for example does not appear to be consistently affected either way by temp or moisture).

I took it to a garage and they said I might need a new fuel sending unit and that would cost $700 to replace but could not guarantee that would fix it. They asked me if I wanted to spend thousands of dollars in repairs because they said it could be so many different problems.

I changed the fuel sending unit myself and also changed the fuel filter. That provided entertainment in the driveway for a couple weekends - didn't make a difference. I removed the console and engine shield and tested a spark plug and it was sparking when I turned the engine over. I tried removing the wire of the top the coil and reseating it - no difference.

How can the van be having such a problem starting when sometimes it starts up immediately and perfectly???

[Matrixx]

Hi ddavis
Welcome to the board. When any shop makes a comment like that (Can't guarantee) tells me they don't know either and fully prepared to start throwing parts at it at your expense. Intermittents are the toughest problems to find (for me anyways), they come and go like the wind. The Important thing here is to "observe" and make mental notes what makes it run and what doesn't. Fuel Level-Altitude-Up Hill-Down Hill-The way the key is truned in the ignition when starting-Making sure you hear the pump boot on start-up-Humidity-Rain.

Something is causing it. Check the fuel pump fuse under the dash. Check the fuel pump relay under the hood, the A/C relay "should" be the same as the fuel pump relay (read the Part# on each) and if they are like my year is, then just swap them around. When was the last tune-up done on the vehicle? When was the fuel filter changed?

Also check for vacuum leaks, very common problem with the front vac lines running across the motor under the hood from the drivers side intake down to the heater control valve located on the passenger side rail under the hood. Please keep us updated, Thanks.

[spongebob218]

Try the "wiggle test" on the coil connector. Not the coil wire to the cap, the electical connector on the coil. I've seen bad connections here a few times. Usually where the wires go into the top of the connector, they are bent and break inside the insulation.

[mikeeFBBB]

How often should the van be serviced? Or after every how many miles?

[gmcman99]

My 99 did the same thing and once I got a major tune up it never had that problem again.
Make sure that original replacement parts are used as some aftermarket parts fail prematurely.

As for maintenance I change my oil every 5000 km and grease all the fittings.
tranny fluid every 50,000 km,rear end every 70,000 km,Use brand name Gas stations for gas.Air filter every 10,000 km.Fuel filter every 30,000km
Monitor the front suspension and steering as they are prone to failure after 100,000 km.
Using this method as having 260,000 km I have still the same tranny, engine, fuel pump.
Front end has fell apart at 100,000 km each time.Water pump failed twice.

I'm using the metric version 100,000 km =60,000 miles

Dan

[kamenz]

Had the same problem-a new rotor and distributor cap solved the problem.

[astro355]

Try the "wiggle test" on the coil connector. Not the coil wire to the cap, the electical connector on the coil. I've seen bad connections here a few times. Usually where the wires go into the top of the connector, they are bent and break inside the insulation.

Also check these connectors for corrosion. Any little bit of corrosion in any connector will give your van a crappy personality of its own. But I would definitely check the ignition connectors first, ignition components are more prone to corrosion problems than your fuel pump. It could be any of the connectors (including the fuses) or even the spark plug wires and spark plugs themselves. I've worked on too many cars were simply unplugging and reconnecting the connectors was enough to remove the corrosion and fix the problem.

Please, please, please, try to figure out the problem before changing parts.

[bobbyjo]

I have the same problem! Will start everytime for up to six months.
Then it will turn over but won't start, no engine codes.
Sometimes it Feels like it wants to fire but dies out.
Sparks plug are getting a spark & wet.
So I have rule out fuel, also it runs okay normally.
If it was the fuel pump, I believe it would idle bad?
So I'm thinking electrical, sometimes I can start it by jumping
a wire from battery to starter motor.(this made me change the fuse link)
Also think it's the ignition switch, but if that was the case! why can't I now jump start it
with the wire straight from battery to starter motor?
Well my six months are up! & it wont start again!
Checked the link, seems okay.
Just don't know what to next?

[paintdrying]

Anyone think this might be a crank position sensor

[RECox286]

Good thought.

Crank position sensors are prone to intermittantly work and not work when they get old and frail. Not much you can do as a way of checking them, other than swapping in a known good sensor.

Of course you have to take into account that the ignition system is usually the bad boy of the neighborhood in, what, say 99% of the cases ?

Intermittants seem to be the bane of the industry, simply because of the engineering complexity of trying to make cars less harmful to the environment, and more fuel efficient for the owner.

Bob

[RECox286]

EDIT: Delete (doggone computer !)

[RECox286]

EDIT: Delete

[1998gmcfasari]

test the batery cabel