Chevy & GMC Vans

Glad you got her fixed! Now you get your van back.

What a great thread! I've been reading all the threads here, trying to isolate the problem with our hard start on our 91, and this one was very informative. Still got some questions though!

When we first got the van, it was running very rough, but it had 6 year old gas in the tank and a blocked cat. No more cat, a new muffler, fresh gas after flushing the tank, new fuel pump and pickup screen, new fuel filter, new plugs and wires, new cap and rotor, new air filter, and a burnt temp sender wire repaired...the results?

Before replacing the fuel pump, it wasn't much better with all the other stuff done. I had to advance the timing 3 degrees just to get it to run even half way decent. Then I replaced the pump, and removed the cat, and it runs awesome now...except it still takes 15-20 seconds to start! And it will only start if you depress the gas pedal about half way! If you turn the key, it will catch and want to fire up, but it won't start without pushing the gas pedal down. And then you have to hold the pedal down for a minute or so to keep the idle higher until it warms up a little, or it will stall.

After about a minute or so, you can take your foot off the pedal, and she idles smooth. And it has all sorts of power now! No more lag in acceleration, no more skipping...and I think I have to bring the timing back down to 0 degrees, because now it seems to be idling a bit too high...if you are in gear at a stopsign or light, she wants to keep going! The transmission wants to keep on keeping on, so you have to shift it to neutral at a light or else the whole van vibrates.

That said, any ideas on why she is starting so hard?

The fuel pattern from the injectors on the TBI look great and even on both sides...although it did notice when I start it without the doghouse or aircleaner in place, fuel doesn't shoot out of the injectors right away...it takes a few seconds for the injectors to start spraying,and when they start spraying is when the engine finally starts.

It almost seems to me that something is telling the computer not to supply fuel right away for some reason...does it sound like any sensors you know about? Maybe the computer is getting a false code, telling it that the engine is already warmed up? By the way, she starts right up when the engine is at full warm-up...if you drive it for a while and then shut it down, she'll start right back up...once it cools down again, its hard start time again!

Help me troubleshoot this please...lol!

I'm going to post this on its own thread too.

Kev

sounds to me like the fuels draining back into the tank after it sits for awhile , like overnight . then the fuel pump is week in supplying fuel to the TBI in the morning . try when first starting the van , just turn the key to the on position twice before you actually start the van , this will let the fuel pump refill the fuel lines & should give you a better start & less wear on the starter . I'd also check your fuel pressure first thing in the morning also to see if theres a difference from a cold start to a warm start . i've seen fuel pumps do some strange things .

the only sensor that really dictates temps to the computer is the coolant temp sensor & you wouldn't believe the havoc it can cause with a faulty reading . its only like a $12 sensor & easy to get to if you want to try it .

Thanks Skippy. I'm thinking it might be the temp sender...I know where the water temp sender is for the guage...where is the one for the computer?

If that doesn't clear it up, I'll put the throttle body and clean and rebuild it, and replace the fuel pressure regulator...but that doesn't seem to be it really...its a brand new pump so the pressure should be fine, and once the injectors kick on, they kick on all at once and it runs fine...hmmmmm...

The mystery continues!

Kev

Under hood, passenger side, front upper engine area, mounted in intake manifold near water outlet. theres a 2 wire connector right in the very top of the sensor .

did you replace the fuel filter ?

I replaced the fuel filter, the fuel pump, the fuel pick-up sock/filter thingy, and even flushed the tank out with fresh gas before reinstalling it...and yep, its a brand new fuel filter.

I think I'll replace the water temp sending unit this week, and give her an oil change while I'm at it...the oil that is in it is OLD...about 6 years old, and not very viscous anymore. It sat the whole time, so its not dirty with mileage per se, just really really old, so I'll change the oil and filter while I'm at it.

I'll let you know if it makes a difference!

Kev