Mechanics

2500 V-8 350 MANUAL TRANS COLD START PROBLEMS

1988 GMC Sierra

This truck is a new addition for me, it has 130,000 miles and is a god truck with the exception ofthis one problem. The problem is when it is cold it just cranks and cranks, until it warms up or the battery runs down. This happens when the outside temp is 50 degrees or below. If I plug in the block warmer over night it cranks up without any problems. It has been put on the computer and no codes, but of course it is warm by then, living way out in country I can't just drop it off. The throttle body has been changed as well as all regular tune up components. If I make a quick trip and lots of stops, it does fine. If my stop is for several hours, now that it is winter, and I can't plug in the block warmer I have to crank it for a long time before it will warm up and then start.
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Samraniam
November 15, 2007.




I, m assuming this is a gas engine right?
When the engine is just cranking what is the oil pressure? When running? Take the air cleaner off, do you have a carb. Or a fuel injector? If fuel injected how many fuel injectors are there?

BTW is this truck realy a 1988? If so, 130,000 miles is very low for a 20 year old truck. How's the body--wanna sell---LOL

Tiny
Pear69
Nov 16, 2007.
Yes it is a gas engine. The 1988 has a throttle body injector so it is considered fuel injection. So has twin injectors into a carb. I have never worked on this kind of set up. Can you tell I'm just a novice mechanic.
I was reading my Haynes repair manual and they mention Model 220 TBI is controlled by the Electronic Control Module (ECM), it monitors engine performance and adjusts the fuel/air mixture accordingly during all engine operating conditions.
This ECM is rather expensive and I don't have the cash to just start replacing components. My thought is that it is not sensing the cold conditions and therefore not making the appropriate fuel/air adjustments, or it is sensing the correct temp but the ECM is defective and thus not making the proper adjustments.
In this system is the: Engine Coolant Temperature (ECT) sensor
Intake Air Temp(IAT) sensor
Throttle Position Sensor (TPS)
The person I bought the truck from said he had it checked out but it never had a code, I am starting to wonder.
I called him the other day and asked about the ECM and he said " Oh, that thing you have to go through the clovebox to change, no I never did that.&Quot; See I bought this truck in the summer and am just now having trouble.

The oil pressure is dead up at 30 when started but the guages don't read while cranking.

OK probably too much info.
Thanks for helping,
Amanda
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Tiny
Samraniam
Nov 16, 2007.
I just read that last line.
The body is in near perfect condition, it came with a canopy and only has 130,000 miles. When it runs the engine hums and I only paid $2500, so I thought it was a great deal, if I could go to town in the winter without having to plug in the block warmer it would be. So for you I would let it go for say $4000. LOL

Amanda

Tiny
Samraniam
Nov 16, 2007.
SOLD! Just kidding I'm not sold on the thought that it's a cold weather problem. What is the weight of the oil? It should be 10w30 or if it's really cold where you live 5w30. Oil must build up some pressure before the ECU tells the injector to let fuel in the engine. When it's cold out oil is thicker thus making it more difficult to flow. Warming the oil makes it flow easier. Your motor has a throttle body on it. This is not a carb. When you press down on the throttle--all you are doing is letting more air into the throttle body. This tells the ECU or computer to let more fuel in the motor. The fuel pump is electric and its located in the tank. When you turn the key it is activated. This pressurizes a fuel inlet line that feeds your throttle body. Any unused fuel returns back to the tank from the throttle body. This system is a TBI system Throttle Body Injection. Take the air cleaner off. The thing that looks like a carb. Is the throttle body. The one or two things in the middle of the TB. Are the injectors. The next time the truck has this condition; have someone crank the motor and see if there is any fuel spraying out from the injectors. The computers in these trucks are pretty reliable and simple, usually lasting the life time of the truck. Not like the computers in trucks today BELIVE ME. Also, It may be an oil pump problem. But lets not panic yet. Did the guy you bought this truck from have the same problem?

Tiny
Pear69
Nov 17, 2007.
Right now it has 10w30, I haven't switched to the 5w30 for winter yet.
Last sunday I got up, unplugged the block warmer got in the truck, turned the key and it started great and drove to church. I didn't take out my extension cord and plug into the outside plug so when I left, 4 hours later, it wouldn't start. One of the guys from church did just that, took off the air cleaner and watched the fuel spray into the throttle body. The truck didn't want to crank so I plugged in the block warmer, went back in and did some work and after 45 minutes, I came back out and it started right up.

The week before the fuse that went to the outside outlet, we added the water trough heater because the water had been freezing at night, blew overnight so my blockwarmer had not had power all night. I cranked it for about 5 minutes and then just walked into town.

The person I bought it from tells me now that it has always had this problem, won't start in cold weather unless the block warmer is plugged in, but it was there extra truck for pulling the livestock trailer so it wasn't a real problem, they never fixed it.

I am in Washington state so the night temps right now are running 30-50, but when it gets below zero I will be in real trouble. If I go somewhere for an hour or less it doesn't cool off completely yet so it will start again easily.

Tiny
Samraniam
Nov 17, 2007.
Ok you have fuel so that's not the issue. You should not have to plug in a block heater to start any motor until the temp. Is below 10 degrees or more. And even then it must be below that for a week or so without any cranking or such.I live in the northeast and last year it was -10 below for a period of about a month straight, I have an 86 chevy 350 T.B.I. And it started right up even after sitting for a day or so outside burried in 4 feet of snow. I never had a block heater in any of my trucks or cars that run on gas. Diesel gells up in the cold and it's those engines--in my opinion--that need block heaters---
Ok that being said lets move on-- You are probably right--and what woman isn't (LOL)--about the ECT (engine coolant sensor). But first when this condition comes up again check to see if you are getting spark. Get a simple spark plug tester. Click on auto parts on this site and go to jcwhitney. Com. Type in spark plug tester and you will see the kind I have. Almost any auto supply store will have these type or simaliar. They are cheap, and anybody who is putting up with plugging in a block heater to start they're truck, can use one.
Changing the ECT is not hard at all. Just make sure that you spray some deep penitrating oil on the threads and let it penitrate for a while before you loosen it. VERY IMPORTANT!-- If the threads break off or the body of the sensor breaks your in for a aggrivating day. CHECK FOR SPARK FIRST!

How old is the battery? If you don't know change it! Get the heavyest duty they make for your truck. Sensors run on very low voltages and if your battery is low or old they can give the ECU a false reading. Also make sure terminals are clean inside and out. Sometimes they have corrosion between the connection and you cannot see it.

Tiny
Pear69
Nov 17, 2007.
Well here's what I finally did today. I took a look at the cap, rotor and plugs and they were all pretty warn so I replaced them and put new wires on also.
Then I replaced the ECT sensor. All this for a total of $114 and 2 hours of my time.
The truck was not plugged into the block heater for 6 hours and the temp was hovering around freezing all day. And it started right up. HIP HIP HORRAY!
Hopefully, no almost assuredly, it will do the same in the morning.
I found in my Haynes a chart for resistance measures across that sensor at different temps and when I checked it was definitely off.
Thank you for walking through this with me and the input you gave, it was priceless. I can go to town without my 100 foot extension cord!

God Bless,
Amanda

Tiny
Samraniam
Nov 20, 2007.
God bless you too Amanda and I must say You may be a-little more than a novis mechanic.

If I helped you please give me a vote or a little feedback Thanks Tom

BTW Don't forget about me if you ever want to sell that AWSOME truck of yours, $4000? Well only if you keep it in good shape
also, if you do need to or want to plug in your your block heater again, use the shortest extention chord possible and make sure it is made with #12 size wire.
I'm an electrician by trade. Good Luck and happy holidays

Tiny
Pear69
Nov 20, 2007.
Tom,

Electrician by trade, I used to be an electronic tech. In the Air Force and then worked for Xerox repairing copiers, now I am an RN, talk about a jump but it is great to have a working knowledge of all types of equipment, human, mechanical and electrical.

The 100 foot cord was my traveling cord, the one at the house is a twenty footer, I guess I can free them both up for something else.

I tried to give feedback and got an error message each time. Is there an engine code for that? Where are the instructions in my repair manual, I can't find the feedback section. LOL

Amanda

Tiny
Samraniam
Nov 20, 2007.

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