Hard Start only when warm H2 2003

[Ulrich1]

Anyone,

My 2003 H2 is hard starting when warm. Only warm everyday. Dealer hooked up computer and said it was a pluged converter, and the scanner showed low battery voltage. Fixed converters and replaced battery yesterday. Today replaced the fuel pump and sender before I return to the dealer. Drove 30 minutes, went to restart-same problem, hard start. The hard start continues to get worse.

I do hear a little air hiss, that started right before the hard start issue. That's what made me think that it possibly was the converter. "Sounds like the air cleaner is off when I hit the throttle". Does a leaky intake gasket cause hard start warm but not cold?

Any suggestions?

[mikejr]

Originally Posted by Ulrich1

Anyone,

My 2003 H2 is hard starting when warm. Only warm everyday. Dealer hooked up computer and said it was a pluged converter, and the scanner showed low battery voltage. Fixed converters and replaced battery yesterday. Today replaced the fuel pump and sender before I return to the dealer. Drove 30 minutes, went to restart-same problem, hard start. The hard start continues to get worse.

I do hear a little air hiss, that started right before the hard start issue. That's what made me think that it possibly was the converter. "Sounds like the air cleaner is off when I hit the throttle". Does a leaky intake gasket cause hard start warm but not cold?

Any suggestions?

Reach out to Hummtech on this forum. He knows his stuff.

[Rico001]

Originally Posted by Ulrich1

Anyone,

My 2003 H2 is hard starting when warm. Only warm everyday. Dealer hooked up computer and said it was a pluged converter, and the scanner showed low battery voltage. Fixed converters and replaced battery yesterday. Today replaced the fuel pump and sender before I return to the dealer. Drove 30 minutes, went to restart-same problem, hard start. The hard start continues to get worse.

I do hear a little air hiss, that started right before the hard start issue. That's what made me think that it possibly was the converter. "Sounds like the air cleaner is off when I hit the throttle". Does a leaky intake gasket cause hard start warm but not cold?

Any suggestions?

Hate to say I have no idea what it is but from all the "miss" information you have from the dealer already it really sounds like they have no idea either.

Please tell me you have an extended warranty and you are not shelling out big bucks at the dealership service department for all the repairs.

I would suggest that you try a auto parts store that does scans for free and get a second opinion at least, and if they give you a print out you could compare it to the dealers if you go back there.
Good luck to you~Richard

[Ulrich1]

Hope they will rescan at no charge. The service advisor was out today.

I took care of the cats and changed the fuel pump myself. I purchased the fuel pump from Bennett Auto for 288.00-A/C Delco. Hummer wanted 400.00 and did not have one in stock. Advance and Napa wanted same price as Bennett but did did not have it in stock.

I'm thinking it is the injectors

[HUMTECH]

Could be a bad ect sensor. If its reading -40c(default temp) and your starting it warm the pcm will see that its cold and demand more fuel causing a hard start. Get them to check scan data and look for abnormal sensor readings.

[Ulrich1]

Originally Posted by HUMTECH

Could be a bad ect sensor. If its reading -40c(default temp) and your starting it warm the pcm will see that its cold and demand more fuel causing a hard start. Get them to check scan data and look for abnormal sensor readings.

I will replace the ect sensor.

Do you know where I can purchase dummy 02 sensor plugs? When I emptied my cats check engine light obviously stays on?

[HUMTECH]

Try Casper Electronics, i got a set of cheaters from thm for my 98 z71. About the same price as o2 sensrs and never had a problem with them

[Ulrich1]

Originally Posted by Ulrich1

I will replace the ect sensor.

Do you know where I can purchase dummy 02 sensor plugs? When I emptied my cats check engine light obviously stays on?

Changed ECT sensor today-No change in starting problem.

[HumminNBoatin']

What codes are you getting, how many miles do you have? When was the last tune up you did?

[HUMTECH]

Agreed, need to get some scan data, codes set? bad cam sensor can cause extended crank, low fuel pressure, too much to diagnose blind. Cheaper for an hour diagnosis time than replacing parts at random

[madmike]

Same problem here. If i turn key on / off three times, it seems to start right up telling me it is probably the fuel pressure regulator or fuel pump. Its like charging the entire fuel line every time you start it. More than likely the fuel pressure regulator or leaking injectors as the fuel pump delivers plenty of fuel and power at full throttle cold or warm. I checked the fuel pressure when running and its close to 40 psi. if it sits for a while it drops to nothing. Pressure regulator may not be holding the pressure in the ports or the injectors are stuck open releasing pressure.

[jsbihn]

Have you checked for a fuel leak?

[HUMTECH]

With engine off, key on and fuel pump commanded on pressure should be 55-62 psi. If you dont have a scan tool to command pump on you can jump fuel pump relay with jumper wire from pin 30 to 87 but dont leave it connected too long. Once max pressure is reached remove wire.

[madmike]

Wait wait wait. it is the fuel pressure regulator. Look up GM fuel pressure regulator repair on Ytube. They have novice tutorials. One video even explains the hard start when warm. Quite easy to repair. I have already ordered mine. Ulrich1, the hiss you hear could be the bad diaphragm in the regulator.

[HUMTECH]

Easy way to tell, remove vacuum line from regulator and plug it, fuel pressure should go up to max pump output

[HUMTECH]

1. Disconnect the vacuum hose from the fuel pressure regulator.
2. Monitor the fuel pressure gauge.
3. Idle the engine.
4. Apply 12?14 inches of vacuum to the fuel pressure regulator with a hand-held vacuum pump.

Does the fuel pressure drop the specified value when the vacuum is applied?
21?69 kPa (3?10 psi)

[HUMTECH]

If it does, you have a poor or no vacuum source. Repair vacuum leak.
If it does not, replace regulator

[madmike]

I think the main problem is that it doesn't hold the pressure. I have measured 45 to 50 psi at idle at the shrader valve. When stopped for a couple of seconds, there is close to zero pressure. If I turn the key three times on and off before turning the engine over there is no issue with quick starts as the fuel pump has recharged the rails. Interesting trouble shooting Humtech but dont have a vacuum pump

[jsbihn]

Ok,
Have you checked for leaks?
I know I sound like a broken record, but if you have a vacuum leak or fuel leak.... well there would be your issue.

Given, you can always got to any auto parts shop and ask to borrow their vacuum pump or gauge.

And also, HT did give you the alternative to a vacuum pump (removing the line and plugging it). Trust me if HT has given you the way, you should follow. He is the ultimate Hummer Guru

(and I know many of us are extremely thankful he is on the forum - Thank You Humtech)

[HUMTECH]

If your losing pressure that fast you likely have an injector leaking or regulator. get it up to pressure and pinch off fuel return line in the braided section. If pressure holds regulator is bad if pressure doesnt hold you have a leaky injector.