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long crank


89blaze's Avatar
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03-08-04, 03:36 PM   #1  
long crank

got an 89 suburban with the 350 TBI. normally, it starts within 1-2 seconds. the past few weeks it has been 2-3 seconds and a couple times 4. just did plugs, wires, cap, rotor, O2, cleaned AIC, fuel filter, air fiter and PCV. runs great just longer starts. would you worry about this?

 
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smogtek's Avatar
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03-08-04, 05:05 PM   #2  
sub - long crank

How many miles?

Can you hear the 2-second fuel pump prime when you first turn the key on?

Might be time for a new fuel pump. Remember, you need BOTH pressure and volume. The pump could be getting worn out. Pumps are good for about 100K under the best of conditions. That means good gas and keeping the tank at least half full to keep the pump cool.

Short of a full on diagnosis, I'd check fuel pressure/volume and go from there.

HTH

Matt

 
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03-08-04, 05:55 PM   #3  
Other that fuel pressure and volume, you need to look at rest pressure and how long it holds. It can lose rest pressure from either end. If you have a leaky injector or pressure regulator, the fuel will leak into the engine. The fuel pump has a check valve in it to prevent the fuel from siphoning back into the tank. Either one of these will cause longer cranking to refill fuel lines and filter. leaky injectors or regulator will also foul the spark plugs temporarily. Another problem with these is having a bad fuel pump relay will cause the fuel pump to energize through the oil pressure switch. This will also cause a long crank but will still run. That will show up on the fuel pressure gauge when cranking. You won't get the 4 second prime when key is turned on.

 
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03-08-04, 06:03 PM   #4  
All good points Desi.

Thanks

Matt

 
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03-09-04, 01:17 PM   #5  
On the '89 burb TBI, it is not designed to hold pressure when the engine is off. The fuel pump should cut on for about 2 seconds when you first turn on the key. You can have someone listen at the fuel tank when you first energize. It should begin pumping again when it gets a crank signal from the ECM. Have you checked the 3 Amp Crank Fuse?
If your fuel pump relay is bad, the pump will not start until you get some oil pressure built from cranking the engine. I don't recall the required pressure, but it is around 4 PSI.

 
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03-09-04, 01:57 PM   #6  
I wouldn't waste my time trying to fix a crank time that increased by 1-2 seconds.Maybe the air temp was a little colder or warmer.If it continues to get worse than it is now and stays that way then I'd start looking.

 
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03-09-04, 02:54 PM   #7  
Originally posted by dirty dan
On the '89 burb TBI, it is not designed to hold pressure when the engine is off.
And just where is it going to go? The injectors are closed and the pump has a one way check valve. If both ends are working properly, it will hold pressure for a reasonable amount of time. If the pressure immediatly drops off, then is is going out either the front or the back. If it's going out the back, it's likely to siphon the entire fuel filter dry and this will cause a long crank. The relay is another distinct possibility but a fuel pressure gauge will answer the question.

 
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03-10-04, 12:22 PM   #8  
Back into the fuel tank.
This is a low pressure (9-13 psi) bypass system. The fuel pressure regulator in this system has an orifice which allows pressure to bleed off quickly when the engine's not running. It will bleed pressure off in just a couple of seconds. It's still a good idea to wrap a rag around any connection before you open it in case your return line is plugged. Too much pressure can also cause a hard start on these TBI's.
On your fuel pump relay connector, you'll see a wire with a un-used connecter on it. This is used to test your fuel pump by-passing the relay and oil pressure switch. If you put battery voltage to this wire your fuel pump will energize. It is useful for checking the pump pressure and volume. Fuel volume is important (OK is 1/2 pint in 12-15 seconds), but if you're running OK after start it's not a factor.
Let us know what you find.

 
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03-10-04, 01:28 PM   #9  
WOW, lots of good info to go on here. Thanks! I think the problem is that my truck doesn't like me. The day I wrote this, it started right up with no prob. After 25 miles at 65mph, I got out of the school zone... I MEAN the freeway, and it started sputtering. It would idle ok but choke out when given gas, like no fuel pressure. Died, and restarted, rapped on the gas to "clean it out" and it ran fine till I got to work. after sitting for an hour, I had a no start-smelled rich so suspect no fire. good oil pres and fuel pump running ( I have 3/4 ton so it runs for 30 sec). 2 hours later, and it starts and runs all the way home just fine. 60 deg durring dying fits and 45 deg when run home if that matters. I assume coil, pickup or module was hot and shut down. I really need to get rid of this and get a truck payment...

Thanks for all the responses and the sparking of debate about fuel pumps. BTW, my fuel pump is original with 250,000 miles on it for whoever said they last 100,000. Hope the pump doesn't go, I just filled the 32 gal tank, which will be gone in 350 miles...

 
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03-10-04, 06:01 PM   #10  
blaze,

Just happened to think about this. I once owned a 1988 full-size Jimmy with a 5.7L. Drivng one day the gas gauge needle started floating all over the place and the engine started cutting out. It finally crapped out for good. I dropped the tank and found the sump box that the pump is submerged in had come loose from the studs it was mounted on. The studs were held in place by compression washers just like the wheels on barbecues!

Anyhow, when the sump box came loose it knocked the hose off the fuel pump and caused the flameout. The box also kept hitting the sending unit causing the wildly erratic needle.

I reinstalled the box using hose clamps and hose over the studs for security. It's too tight to get a die in there to thread it for a nut! Replaced the pump and I was good to go!

BTW, GM had a service bulletin out on the problem.

Just a thought.

Matt

 
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03-11-04, 01:43 AM   #11  
The gas gauge is fine, except that it drops too quickly. You would think a 32 gal tank would go more than a week on $50.

I am down to a coil or a voltage drop on the power wire to the coil. It started off acting like a fuel prob and has reared an ugly electrical head.

 
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03-11-04, 07:08 AM   #12  
Originally posted by 89blaze

I am down to a coil or a voltage drop on the power wire to the coil. It started off acting like a fuel prob and has reared an ugly electrical head.
That's really strange. I've never seen ignition cause a long crank except in the case when it was firing off the cam sensor instead of the crank sensor. I don't even remember which vehicle that was possible on now. There was one.
That should be easy enough to just use a jumper wire to test it and eliminate that possibility. Even a normal spark tester will tell you if anything like that is happening but i really doubt it.

 
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03-11-04, 11:23 AM   #13  
Well, the problem has grown into a weak spark condition causing intermintant no starts or crappy running. This is where I am going now and hopefully the weak spark was what was causing the slow starts.

 
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03-11-04, 02:23 PM   #14  
I ran into this before and the coil passed every test I could think of it just didn't always fire right.I also checked it with an hei spark tester and it passed but it was bad.I would be tempted to try a coil myself but thats me,once in a while I take a hip shot.lol

 
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