Hard to start after sitting for 2+ days

[lunytnz]

My 99 with 5.7L has become difficult to start when it has been sitting for a couple of days, or more. Normally, I'd say I crank it for about 1 second and it fires right up. When it has been sitting for a couple of days, and I crank it for 1 second (I let off the starter out of habit), it seems to fire on a couple of cylinders, but that's it (it's like I *almost* cranked it long enough, but not quite). I can try cranking it for 1-2 seconds 5 or 6 more times and it won't start. If I crank and hold it for at least 5 seconds, it will finally start. When driving it daily, or maybe letting it sit for one day, it starts right up with the normal crank time.

 

The last time this happened, I just kept cranking after the first attempt. It took well over 10 seconds of cranking, but it finally started. It kind of reminds me of the 'vapor lock' symptoms of the 70's.

 

Anyone had a problem like this? Any idea what's going on?

 

I first noticed the problem this summer, during a camping trip, so it's not a cold weather issue.

[00Silverado4x4]

Have you tried just turning the key to "On", let the system reprime, then try to start? If it fires right up I'd say your fuel system is losing it's prime. Also you could have the battery load tested. Your battery might be getting weak.

[Wolfmanjohn]

I'll second '06Sierra on begining with the fuel system. Those symptoms were the earliest warning I got of the impending fuel pump failure on my '99 'Hoe 5.7. Then again, gradual fuel system pressure loss can be as simple as a worn/faulty gas cap.

[waumo1]

With no more information, I would also guess fuel pump. My brother in law just had the same symptoms on his 1999 or 2000 CK with 5..7 and replaced the fuel pump for a cure.

[wavery]

I would guess f/p or fuel pressure regulator. When was the last time that you changed the fuel filter?

[lunytnz]

Thanks, all, for the replies. The fuel filter was changed out last year, so that *shouldn't* be the problem. I was wondering about fuel pressure. I had the fuel pump replaced about 8-9 years ago as an (incorrect) attempt to fix the problem with the fuel gauge, so it's not the original.

 

I hadn't thought about the fuel cap. I realize the system is pressurized and that the fuel pump is engaged when you turn the key on. So, the next time I try to start it after it's been sitting for a few days and it doesn't start after the normal crank time, I should turn the key back to on for, say 10 seconds? If it starts during normal cranking after that, does it likely mean that the fuel pressure is dropping way down over a period of 2-3 days? Is that what you mean by "losing its prime"?

 

Maybe a fuel pressure tester is the right next step? I would have to buy one. Do you just attach it at the fuel rail and test the pressure there? Is the pressure regulator an easy part to get at on this model year?

 

The battery is not new, but I figure if it can crank for 10-15 seconds, it's still in good shape.

[wavery]

You didn't say how many miles that you have but if it is a high mileage engine, sitting for a few days will allow most of the oil to run off the cylinder walls and rings. You could be starting to experience low compression at start up.

 

You may want to perform a cold compression test after the truck sits for a few days.

 

If you can crank the engine for 15 seconds, it's not a low voltage issue. The voltage only gets lower as the engine cranks, so you have higher voltage the 1st few seconds. You say that is has to crank longer then it starts, so that's not the issue.

[00Silverado4x4]

Yup that's what I meant by losing prime. As far as exact hook up to check pressure I'm not sure but it sounds right to hook up to the rail. Sorry I can't really help you on the rest of your questions. I'm stilling reading the Chilton's to learn about my truck. Most of what I've learned about GM trucks has been from this forum.

[lunytnz]

This problem has continued from time to time over these many months. It does seem to be getting more predictable after it has sat for a few days. I finally got a fuel pressure tester and hooked it up before I started it (I think it's been sitting for 4-5 days). I was kind of surprised to see the fuel pressure come right up to just over 60 PSI when I turned the key on (so it seems to be priming just fine). While cranking, the fuel pressure stayed above 60. When it finally started, it ran rough for a about 15 seconds before smoothing out. While running, the fuel pressure is about 54 PSI.

 

One thing to note: when I first tried to start it and cranked for the usual 1-2 seconds before 'letting go' of the key, it seemed like it kept firing a single cylinder every second, or so (kind of like dieseling, but much slower than I'm familiar with--the engine wasn't really running at all). It fired 5-6 times before I finally turned the key off.

 

BTW, it took me a while to find the Shrader valve because it's hidden behind some hoses, but it's on the fuel supply line near the rear of the driver's side valve cover (in case this helps someone else).

[lunytnz]

You didn't say how many miles that you have but if it is a high mileage engine, sitting for a few days will allow most of the oil to run off the cylinder walls and rings. You could be starting to experience low compression at start up.

 

Yikes, wavery! That's kinda scary (especially approaching Halloween as we are :-) but you could very well be right. It has over 160,000 miles on it.

[Bad Bowtie2]

1st thing one moring try disconnecting the line to the fuel pressure regulator. If it is wet with gasoline, replace it with a new AC Delco unit.

 

Then report back to us the next moring you try and start it...

[Debo511]

1st thing one moring try disconnecting the line to the fuel pressure regulator. If it is wet with gasoline, replace it with a new AC Delco unit.

Then report back to us the next moring you try and start it...

 

 

What he said.

[lunytnz]

I've had a hard time figuring out exactly where the fuel pressure regulator is, despite having BOTH a Chilton manual and Factory Service Manual. I just can't find a decent diagram in the FSM that shows where the regulator is.

I *think* it's on the driver's side top of the engine, but it has a breather tube to the valve cover (which the regulator on my older GM car doesn't have).

I think you mean to disconnect the vacuum line to the pressure regulator--that's connected on the side, right? About a 1/4" diameter black tube kind of pointing toward the left-front of the truck, right? When I disconnected that (and it's hard to get off), I didn't see any fuel come out.

Also, I can't find in the manuals where it says what the fuel pressure is *supposed* to be. Is 60 PSI too high? Or normal? In my other GM car, the fuel pressure is supposed to be about 40 PSI. What kind of problem would too high fuel pressure cause? Would it make the engine hard to start?

Thanks for the help... sorry for the delay in replying (been out of town).

[lunytnz]

I started it two separate times in the past week after it sat for more than 3 days each time. It fired right up each time, so that makes me think it's not as likely it's a compression issue because low compression would be a pretty consistent thing, right?

[Michaelj42]

I believe fuel pressure should be between 55 & 65 on this engine. I have the same year/engine and mine is typically ~62.

 

Here is a good video on fuel pressure problems on this truck:

 

 

(From the description) They go over:

1. How to test a fuel pump relay in a power distribution box.

2. Power side switched circuit design description and operation.

3. Bias voltage on an output. How and why is it used.

4. Fuel pump power and ground testing.

5. How to manually jump a fuel pump from the fuse box

6. How to measure fuel pump current flow.

 

I am not in any way connected with those who made this video, I just found it interesting and helpful.

 

I am having the same trouble with my truck. Another thing that I have checked so far is the Engine Coolant Temperature sensor. It is in the front of the engine, near the thermostat. It can be checked by taking an ohm reading on the sensor leads. Your Chilton's should have the correct resistance for various temperatures. You can also check the wires of the lead to be sure you have 5 volts there.