Big E

I know this is not a boating topic, maybe it is because I use my truck to pull my boat.

Anyway - I have a 99 Chevy Silverado 5.3L 1500 4wd, It does not want to fire right away when the engine is cold. The engine turns over and turns over and turns over then fires, it runs rough for about 5 seconds and then runs fine. The truck runs fine on the Highway, no problems, and it fires fine when the engine is warm.

I did the obvious, replaced the fuel pump and the fuel filter, but it still does this. I now think the maybe the fuel is draining away from the throttle body when the truck sits for a while (overnight). Any suggestions would greatly be appreciated. No one seems to know.

Before I replaced the fuel pump I took a reading on the fuel pressure and it was low, and my gas guage would be eratic on a full tank of gas. So I assumed it was the fuel pump. Now with the new fuel pump the gas guage works fine, but the engine still is hard to start cold.

ido1320

Hi E,

The fuel draining away is not very likely. Your fuel pump should run for a couple of seconds when you hit the key to pressurize the system. You could eliminate that as a possiblility by cycling the key a couple of times and then trying to start it. To me, it almost sounds like a cold start enrichment issue. A good place to start would be the ECT (engine coolant temp) sensor, generally located on the thermostat or somewhere close or possibly the IAC (idle air control) located in the throttle body. A mechanic with a good scan tool could be a HUGE help on this. With out seeing it, it can be a hard one to diagnose. Wish I could be of more help.

Vinny P

I can add a little to what was said above. Although there is a check valve in the tank unit, I have never seen fuel draining back in an injected motor, so I don't think that is your problem. What can be happening is the pump relay may not be powering the fuel pump with the hit of the key. Go to the fuel pump relay in the " Underhood Electrical Center" Pull the relay out, look at the bottom of the relay for the #30 pin, it is a gray wire under the fuse/relay box. This wire is your hot lead to the pump. Attach a test light to it, have someone go in the truck and turn the ignition to run--don't start it. The light should illuminate for a few seconds. If not, check for power and ground ( with the ignition on ) to pin # 85 and #86. I don't remember which is which but it is easy enough to tell. There should also be constant power to pin #87. Let me know what you find, I can hopefully tell you where to go from here. I can also send you wirning diagrams if you need them..

delsol

Sounds like you know your stuff on these trucks, how about the M30 trannys, and transfer cases? I'm just about ready to take mine to the scrap yard

Big E

checkmate454 - I checked the fuel pump relay location and I was a little reserved to pull it out. I'm not real sure how to get it out. It is a little box next to all the other fuses. Does that just pull out like a regular fuse? And also when I get it out, put the light on the pins it connects to?

Vinny P

BigE,
Yes, just pull the relay out. It will be a little stiff, but there is nothing holding it in, but a little pressure from the pins. When the relay is out, you will see numbers under the relay which correspond to the pins or flat tabs of the relay, that plug into the relay box. It is in the box where I need you to check for power and grounds as I stated above.

Airpacker

99 5.7 with mpcfi hard to start cold huh. Those engines are famous for whats called poppet valve injectors sticking causing a flooding condition after a long rest period. Your comment on runs rough at first is a little hint here. Does the exhaust smoke black after start up? Does the truck idle fine when warm(no intermittent miss)? As far as checking the fuel pump pre run condition,its easier than screwing with the relay. Stick your ear to the box of the truck and have someone turn the key to the RUN,not crank position. You should be able to hear the pump run for 2 seconds then stop. If so,forgat the fuel pump,have the system scanned for long term fuel trim numbers,if they are low,expect to be opening the manifold up and replacing the spider assembly.

Big E

Airpacker - Yes to all of your above questions, I'd hate to take it to the dealer again to get it scanned. They charge $98 to scan it. They did it the first time and told me it was the fuel pump. So I changed it myself. I really don't want to do it again and then have them tell me it is the "Johnson Rod" who knows with them as long as the register keeps on ringing the money up it seems thats all they care about also they would probably say that I installed the pump wrong because they didn't do it, which I didn't.

You are talking about the spider assembly, what is the cost for that? Also how come the check engine light has not come on yet for things like this? I thought that is what it is for.

Airpacker

First of all,find a good independant shop and build a trusting working relationship with them. Any well equipped and trained shop can diag your problem successfully. Dealers are notorious for underpayig their techs for diag time so it doesn't always get tested thoroughly. Believe me,a major part of my business is re diagnosing vehicle failures after several trips to the dealer. I am not going to tell you ALL dealers are this way but there is a load of them. As for the M.I.L. light not coming on,there are several factors that must be met before the powertrain control module will set a service code and illuminate the light. Each factor has a operational window which is assessed by the pcm. You can have failures that stay witihn the window,thusly no light. A spider is not cheap but if you do end up in need of poppets or a spider,contact Jim Linder at www.lindertech.com. He is the leader in remanned units and ships anywhere from Indianapolis.

Big E

I wish Toronto was a lot closer to St. Louis, I would be taking my truck to your shop. You seem pretty knowledgable, and it also seems like you give a damn. Most shops really don't.

As far as my truck, after I changed the fuel pump last Wednesday, it was still hard to start. This past Saturday, I took the truck on a 6 Hour drive, and I have noticed after that, it seems a lot better on cold starts. Now that I wrote this, it probably won't start this afternoon. (Thats the way my luck runs) I did have fuel injection cleaner in the tank before my trip, and I ran the truck to almost empty, maybe that helped. I don't have a lot of faith in those type of cleaners though. But for right now my truck seems to be fine. I will keep you posted. Thanks for your help.