2001 5.7 vortec, chronic starting problem


68ragtop
12-29-2009, 07:21 AM
Hi Guys, This is a long term illness on a 92K miles 01 express.

This van has always (as long as I have had it) started hard. What I mean is, it cranks
probably three times longer than it should from a cold start. Runs great otherwise.

But, the real catch is, in odd weather like cold, it will not start at all. This is ver intermittant. But it will act as if it is flooded. Crank with some poping out each end.
Leave it sit & then next day it might start right up like nothing happened.

It seems to me it is misfiring, but it doesn't set any hard or soft codes. Last spring I replaced all wires, plugs, cap & rotor, fuel filter. Thought I would be good for this winter, but I am stuck again today. (about 10 degree's here)

Could this be a crank, or cam position sensor? Any ideas? I am thinking the long cranking on startup might have something to do with it, but its got me stumped......

MT-2500
12-29-2009, 10:01 AM
Sounds more like secandary ign.
Check cap and rotor and plug wire and coil for good hot blue spark to all plugs.
Always check for lose of spark or fuel pressure when it no start.
Did you use good AC delco cap and rotor and plugs with tune up?

68ragtop
12-29-2009, 10:27 AM
Just pulled the doghouse off & was able to do some testing seeing it will still not fire. For the first time, I do have a noticable symptom. When checking spark from the coil wire (before the cap) the pulses are random. There will be steady pulses, then one here & there & more random, Then steady again.

are the spark pulses generated from an ignition module on these?

Carl

68ragtop
12-29-2009, 11:22 AM
I can now rule out the crank position sensor, just replaced that & the spark is still random.

Whats left?

MT-2500
12-29-2009, 11:43 AM
Why did you replace crank sensor?
Check ign module and ign coil.
Any codes or check engine lights?

68ragtop
01-11-2010, 07:45 AM
Well, happened again & I am getting drained......

Always happens when its cold, usually high humidity I believe. Its lightly snowing right now
& about 20 degrees.

I have a timing light connected & have been checking for spark with that everytime I start it. This morning it had spark, did the usually "too long of a crank" then sputtering now I am sure its on its way to being flooded again. This all within less than 10 seconds of cranking.

25% of the time this van will crank 3X too long for a vortec. No matter what the weather is. This is random. But as soon as It get to the point where it normally will fire, it either starts right up, or sputters a little & is flooded.

I have now changed the wires, plugs twice & cap/rotor twice in the past few weeks, & the crank sensor.

I was quite sure it was not sparking on start up & thats why it was flooding, but this morning it has spark, but wouldn't start.

What now, should I replace the ECM?

68ragtop
01-11-2010, 10:00 AM
Just a quick update from 2 hours ago. . Pushed the van back into the shop, Pulled a plug & it's a bit wet & smells of fuel. So, all of this in under 10 seconds of cranking this morning. I only cranked it as long as it usually takes to fire, when it didn't I knew it wouldn't happen, so I pulled the fuel relay & tried again holding the throtle open hoping it would clear out.... Nothing. Pulled a spark plug & its wet, not fouled, but wet around the arc tip. Now, givin that info, I had a timing light wired & on when I first cranked it up. (I have been doing this everytime I start it) I did have spark.

Sooooooo, how does an engine flood in 8 seconds of crankling, with spark?

BTW, I did test this plug I pulled & it had a nice blue spark, even with the fuel on the electrode

MT-2500
01-11-2010, 10:32 AM
Throwing parts at it will not fix it.
Proper testing will tell you the problem.

If plugs are wet on end or gas fouled replace them.

Check for good hot spark to all plugs.
Check for proper fuel pressure/
As asked before in upper post.
Any check engine lights on when it is running?
Is engine cranking over good?
Will it start with a shot of carb cleaner?
The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

68ragtop
04-01-2010, 04:07 PM
Well, I am back to testing this again.

What I have ruled out is spark. It has spark durring these hard starting episodes.

Now I have been drivig it with a fuel pressure gage hooked up all the time. With the return line temp. blocked off, the pressure climbes to around 75 lbs. Otherwise open, it is usually around 60lbs. As MT-2500 mentioned it does idle around 61 lbs & goes up as I put a load on the engine.

Now, I finally was watching the gage today when it started hard.

I drove the van about 16 miles to a jobsite today where it sat for about 5 hours. I jumped in it, watched the gage as I started to crank it. The pressure slowley came up as it cranked. This was one of those long cranks I talked about in earlier posts. Once the pressure hit 60lbs, it started. This must be my problem? It very intermittant though, most times the pressure jumps right up & it fires within 1-2 seconds as it should.

These long cranks are about 4-6 seconds of steady cranking.

MT-2500
04-01-2010, 06:07 PM
You need up around 63-64 lbs to squirt injectors cold.

Slow priming can be several things.
Weak fuel pump or clogged sock or fuel filter or wiring and voltage to pump or pressure regulator leak off or slow pump relay.
A good strong pump should dead head 95-105 lbs of fuel pressure.
How old/mileage and what kind of fuel pump do you have?

Do you keep over a 1/4 tank of fuel in it.

Some people with slow primers just flip on the key 2-3 times before trying to start it.

68ragtop
04-01-2010, 06:40 PM
Original fuel pump & the Van has been doing this sinse shortly after I bought it back in 2005. It had about 61,000 on it then. It now has around 106,000. Problem hasn't really gotten any worse, or better. However, I have replaced the starter once due to the excessive cranking. Really only causes big problems when its really cold out. 0-20 degree's. 85% of the time it starts normal.

MT-2500
04-02-2010, 08:43 AM
Original fuel pump & the Van has been doing this sinse shortly after I bought it back in 2005. It had about 61,000 on it then. It now has around 106,000. Problem hasn't really gotten any worse, or better. However, I have replaced the starter once due to the excessive cranking. Really only causes big problems when its really cold out. 0-20 degree's. 85% of the time it starts normal.

Check fuel filter.
Check fuel pump wiring harness at transmission crossmember.
A lot of plug in there I have had to rewire there for poor connections.

Also hook a volt meter to gray wire at rear to fuel pump and watch voltage when slow to prime.

Let us know how it goes.

68ragtop
04-02-2010, 09:13 AM
Fuel filter has been changed twice over the past 5 years. Never seemed to help at all.
I assume the gray wire is the + feed to the pump? I will tap a wire into it & keep a volt meter in the van & follow it. BTW, the tank is usually between full & quarter tank. Never really goes below 1/4 before it gets filled again.

Thanks

68ragtop
04-20-2010, 07:36 AM
So far no voltage drop at the fuel pump, just random slow pressure build.

Should this system be able to hold pressure for very long after the initial fuel pump cycle on start up? Even on the "normal" starts If I just turn on the key, it will cycle up to 60+ lbs, but then will drop right back to zero with in a second or two.

I am going to get this recorded & post a video so you can see a video of how it acts.

MT-2500
04-20-2010, 08:36 AM
So far no voltage drop at the fuel pump, just random slow pressure build.

Should this system be able to hold pressure for very long after the initial fuel pump cycle on start up? Even on the "normal" starts If I just turn on the key, it will cycle up to 60+ lbs, but then will drop right back to zero with in a second or two.

I am going to get this recorded & post a video so you can see a video of how it acts.

You need 63-64 lbs engine cranking to squirt injectors on a cold start.
Always check/watch engine cranking pressure.

Low pressure and fast leak down and slow build up run the full fuel pump presure test.
The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

68ragtop
06-24-2010, 03:12 PM
UPDATE:

Problem solved after years of issues.......

Last week my fuel sending unit started to read incorrectly. So, I had to pull the tank & I replaced the fuel pump/tank unit. Turns out the fuel pump was the casue of my chronic starting problem.
Now, with the new pump, the pressure jumps to 60psi within 1 second of turning on the ignition. it also holds the pressure after the pump stops cycling. The old pump took twice as long to get to 60psi & when the pump would stop, the pressure would drop right back to 0 psi within a couple seconds. Start faster than it has for as long as I have owned it (5 years) & it idles smoother too.

68RT

MT-2500
06-24-2010, 05:01 PM
Thanks for posting back how it went.
Did you run the fuel pressure test as outlined?
If you did you should have found the problem.
Also good idea to check the pressure after replacing the pump.
You should see 64-65 lbs. prime up and engine cranking.

If you used a Delphi fuel pump instead of a junk Airtex you should be good to go.

68ragtop
06-24-2010, 06:51 PM
I never got a chance to plug off the return line a second time, so I didn't get that. I had only monitored the voltage. I bought a used assembly from a low miliage wrecked express. I figured a GM one used was way petty than any aftermarket unit. Thing was, from day to day the van ran fine. Its used in the service feild every work day & for the most part, it always ran fine, just would excessivly crank about once every 6-8 starts.
One of those nagging things that I just put off.

Glad its cured, it seems to run better than it has in the past 30K miles.

Thanks for all your help!

68RT

MT-2500
06-25-2010, 08:52 AM
I never got a chance to plug off the return line a second time, so I didn't get that. I had only monitored the voltage. I bought a used assembly from a low miliage wrecked express. I figured a GM one used was way petty than any aftermarket unit. Thing was, from day to day the van ran fine. Its used in the service feild every work day & for the most part, it always ran fine, just would excessivly crank about once every 6-8 starts.
One of those nagging things that I just put off.

Glad its cured, it seems to run better than it has in the past 30K miles.

Thanks for all your help!

68RT

You are welcome and good luck.

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