[FallstonYJ]

Hi folks! New here as of today. Just bought an 01 Jimmy for my wife; (she LOVES it!), and have a couple of issues I'd like some input on please. I will start a new post for each issue.

First issue is with starting. In the morning upon first start it fires up instantly and runs great. After that, with no real pattern that I can discern, randomly it will take 5 seconds or more cranking for the truck to start. Once it starts it again runs great? I've had some people say it's the fuel pump and fuel is leaking down but that doesn't add up since when it sits overnight it fires up instantly. I changed the fuel filter last week but that hasn't helped at all.

Any advice would be very much appreciated!

Thanks for your time,
Tom

 

[Dana W]

Does it still turn over as strong as when it's cold started? If not, y0u may have a corroded ground connection somewhere, or even some light oxidation on the battery posts can do it. When it's hot the added resistance of the oxidation can cause a power drop to the ignition system. I have this issue with my '99 'Burb. About once a month, I have to clean off both posts on my battery with a wire brush even though I can't see any oxidation, otherwise, when the engine is already hot it acts like the battery is dying. It may not be your issue, but it could be.

 

[RayVoy]

If the connections are good, it's probably fuel, or spark. I pull a sparkplug just before trying an afternoon start, check it for raw fuel. Even if it's dry, there could be a fuel problem, but if wet, you do know there is a bleed down of fuel.

 

[FallstonYJ]

Thanks for the replies!!

The battery and connections seem to be in good shape. Haven't had a chance to pull a plug yet. It was -20 with wind chill yesterday and not much better today! I had a buddy of mine who is service manager at Sears auto tell me that he thinks it may be the starter. He said the 4.3 has a high torque starter and when they start to go they will not crank fast enough to start the vehicle quickly?? Anyone else heard of this?

Thanks again,
Tom

 

[RayVoy]

All I can add, is that I've had a couple of 4.3s, I've ran them to over 300,000 and never had a starter fail. The 4.3 is the 5.7 less a couple of cylinders. It would seem, to me, that GM would have used the same starter in both engines and 6 pistons should be easier to spin than 8.
These starters do require a heat shield, without the heat shield thhe starter will spin slow when hot.

Does the engine seem to be spinning slow?

If you have a heat shield, I'd be suspecting a bad battery.

 

[the phantom]

Yeah a bad cell in a battery will do what you are describing. I had this happen in my new truck after only a year old. If you dont find the problem soon it will/may begin to get worse if it is the battery.

 

[Bowtied]

check not only your connections but also your bolts make sure your bolts are nice and tight i think the starters ground out on the starter body so a loose bolt on the starter is like a loose ground.

 

[the phantom]

I hope after 2 months he found the problemIf not hes probably not going to

 

[ck309]

I would definitely take a good look at the fuel pump. If the pressure is off any it will cause inconsistent issues with starting. I have a 2001 jimmy and had the same experience. I replaced everything suggested without a cure. It got progressively worse, I started having to use starting fluid and that stopped working. With the fuel pump working, it being off a bit wasn't considered by many, even "certified" GMC techs. Truck runs fine now with new pump. Starts the way it should. Keep these fuel filters changed out regularly.

 

[FallstonYJ]

I hope after 2 months he found the problemIf not hes probably not going to

Still having the same problem and still haven't figured it out?? Only change is that it doesn't necessarily start quickly first thing in the morning anymore. Now it can take 5 seconds of cranking plus or minus first time or at any given time thereafter? I have just decided to live with it until it won't start at all and then figure it out. I know that's probably not the best way to handle it but I haven't had any luck figuring it out!

 

[ck309]

Its THE FUEL PUMP...I promise..It will work intermittently and drive you crazy trying to figure it out. If the fuel pressure is off just a little it will work, but not always. I have a 2001 jimmy, I spent a year with this issue, it will get worse as time passes. Some local mechanic finally figured it out, after I had wasted time with those "GMC certified" mechanics. Its not enough to hear that the pump is working, when he checked the pressure it wasn't off by much but it was enough, he said he had never seen one do that with such little press drop. Replaced the pump and all was right with the world again. I had replaced many ,many parts without any results, damaged my air intake spraying starting fluid to start.. which will work for a while but I DO NOT recommend, unless you like the sound of cannon fire under the hood, and then you get to pay to fix those damages......those were fun times.

 

[FallstonYJ]

Thanks for the reply ck309 but not the fuel pump in my case.

My mechanics at Sears Auto; (yes, that's right.......Sears Auto in White Marsh, Md are the best in the business!), figured out that it was the fuel pressure regulator. After replacing the regulator the Jimmy starts instantly every time!!

 

[RayVoy]

Pumps either pump, or don't pump, it's the regulator that controls the pressure.

And, I know I will have a few disagreeing with me; yes, a pumps wear and, or, start to leak they may pump below the threshold, I'm talking about good working pumps.

 

[estrom]

Would the fuel pressure regulator also fit the opposite scenario? My problem is reversed...it is VERY hard to start in the morning (good battery, cranking fine, just refuses to start) but once it does, it runs fine and starts fine the rest of the day. I'm typing this now in the AM because it actually won't start this morning.