cold start

hi hello am new to this form would like to ask for some help so if any one has had this kind of problem please toon in. what i have is a 99 taco with a 2.7 4cyl whin it gets cold 33 or below it will not start . it will turn over just fine , ive had it at 2 differnt shops 800 bucks later still no start . no engine codes flash. the last thing they said is it must be down on compression so they want to put new top end for 1600$ and no promis that will fix . i said no. ..... any thoughts ?

 

"Must be down on compression"? That's an easy test to do. Find another shop. They need to be sure of what's going on before they tear your truck down.

Does it run fine once it's started?

I'm not too familiar with these engines but I know there is a coolant temp sensor and there may also be an intake air temp sensor. I would suspect one of those is out of whack and the computer is not giving the engine enough fuel for a cold start. This should be something a good mechanic can monitor with a scanner. You might have to leave it with them overnight so they can work on it cold.

I doubt the compression story. I have driven some pretty whipped vehicles and never had an issue starting them on a cold morning.

If you have a dealer local to you it might be time to give them a chance at diagnosing this. The labor rate per hour may be high, but they are probably your best bet at this point.

Tell the next shop you use that you want the cold start issue fixed and you are going to pay for that result only. What did they do for $800? That's a lot of money for no results.

 

That compression story deserves a kick in the balls for trying to take your money.

Cold weather can cause a electrical connection to shrink just enough to not make contact.

Pretty much need to check for fuel and spark when it is giving you the no start symptom and go from there.

You can do this yourself with a fuel pressure gauge and by pulling a plug to check for spark.

Keep it simple and start with the basics.

 

i checked the spark with a difert plug it was really good there is not a tire valve any where on the fuel rail might b able to splice a presure gage in the bypass hose will it give the full pressure or only the pressure of whats bypassed . i turned the key on should u be able to here the pump kick on? will give it a nother shot in the morning thanks for the input.

 

I am have not owned or worked on a 4cyl to know if there is a schrader valve for checking fuel pressure.

Just hearing the pump kick on or hum will not be enough to know if there is enough pressure it has to be checked at the engine.

When do have the cold start problem on possibility is to pull the plug after it will not start and see if you are getting any fuel at all on the electrode, but as stated it still needs to hit the correct pressure to atomize the fuel.

 

once you had it running and its warm, you can shut it off and get a shop to do a compression check or you can yourself if you get the tools, just pull out one spark plug at a time (so its on 3 cyl) the start it for just a few sec and you could get a reading of its compression, but for the life of me i cant remember the specfic name of the tool that you use, but im sure some people that know more than me would know if you mention that to them, Hope this helps some.

 

http://www.tacomaworld.com/forum/4-cylinder/187464-perhaps-fuel-problem.html

Looks like not schrader valve you will need to wrench a lil to just read the fuel pressure.

 

also maybe your ECU is going bad and doesnt like cold weather. Also make sure you find someone who may know for sure bc if you say ECU to a shop there gonna rip you on money. I had a 4cyl Ranger before my Tacoma and i had some problems with it ( it was a 91 with 180,000mi on it)

 

Crankshaft sensor !

 

thanks for the picks and info . whin i turn on the key i do not her the pump at all

 

Temp related problems are usually temp sensor problems. With a faulty sensor, the mix can be so far off, it won't fire up.
Check the intake and coolant temp sensors for proper operation.

 

well good comp in all cyls. good fuel presur when turning over , none with just the key on . the only temp sensor i could find was the water and the exahust. no one had the exh instock, it was above 40 so it started just fine today

 

u need to remove all the plugs before u crank the moter to do a proper comp test (compression gauge) i have one thanks for ur input

 

^^^^^^^^^^^^

 

Could be. Could also be a temp sensor as discussed above.

My two cents:

I believe the key to figuring this out is to have a scanner hooked up to it when the problem is actually present. If there are no stored codes, you should be able to monitor what the temps are at cold start and make sure all the readings are believable. And the crank sensor signal should be able to be seen on the scanner also.

If you can't rent a scanner or borrow one then your best bet is to find another shop that has their heads screwed on straight and will work on it cold. I seriously doubt it's going to take anyone who is competent more than an hour to diagnose with the proper equipment. Changing parts that you can't prove are defective is going to continue to cost you money.

 

This!

Proper troubleshooting involves duplicating the problem, finding the exact cause of the problem with meters, gauges, etc, then repairing. Swapping out parts to find the problem is very expensive, time consuming, and normally won't solve the problem.
Parts swapping mechanics are the bane of shops everywhere. Find a troubleshooter, not a parts swapper.

As for the crank pos sensor, odds are poor that it's the culprit. The op has a specific temp problem. Crank sensors usually fail intermittently or completely. Sometimes the become loose and become completely erratic. I would focus on temp sensors. Test em and prove they are bad, then replace as necessary.

 

it only happes when it is cold. other wise it is fine runs like a top no hicups no crank crank crank so i think it has to be a cold start senser of some sort i just cant find one any wher on this pu. i guess it is off to toyota. thanks for all of help. if they find out what is wrong i will post it.

 

Air intake temp and coolant temp govern fuel mix. There are no other temp sensors that influence starting.