Hard starting when hot - Page 2

rkvons · #16 10-28-2008, 01:51 PM

I have pulled the vacuum line off of the fuel pressure regulator and did not see any gas in it. If the line is left off, what will it be like to start it? For the other CPS that is on the back of the engine, I've tried to locate it and was not able to. Does anyone have a diagram of where that is? One last question: Where is the TPS? Maybe it needs a cleaning. Thanks.

merc81 · #17 10-28-2008, 03:32 PM

I'm convinced you are wasting your time going after the crank position sensor in the rear, but its mounted on the oil pan, right behind the exhaust pipe. It has a little metal shield over it to protect the connector. It comes out by removing the metal shield and a keeper screw that clamps the sensor in to the oil pan. Its a tight fit with an O ring through the pan. The wires from it go directly up to the coil pack and are twisted. I recall them as being black and yellow with a plastic flex cover over them to protect from the exhaust heat.

There just doesn't seem to be any way that this sensor could cause the engine to act like it wants to 'hunt' and not idle correctly. It runs the timing on the coil pack. A code would set should it fail.

** tps is just under the IAC. Look in the photo above; its got 3 wires on its connector.

John

rockwood84 · #18 10-28-2008, 07:58 PM

when you pull the tps out to clean it ,make sure nothing is broken on it. if it is working properly you should be able to ohm it and watch the resistance it should move the numbers as you move the tps back and forth .if the numbers don't change then its bad. and when you put the old or a new one back in make sure you get it in the notch or it will be off.there is a notch on the throttle body and a groove in the tps.center the notch in the groove.

rkvons · #19 10-29-2008, 09:23 AM

Quote:

Originally Posted by merc81

I'm convinced you are wasting your time going after the crank position sensor in the rear,

I'm not going after it for this problem. I just heard a while back that this is a possible source for an oil leak and my engine is wet on the back side. I tried to locate it to see if the o-ring was dried up and was unable to find it at the time. Thanks.

rockwood84 · #20 10-29-2008, 10:13 AM

Quote:

Originally Posted by rkvons

I'm not going after it for this problem. I just heard a while back that this is a possible source for an oil leak and my engine is wet on the back side. I tried to locate it to see if the o-ring was dried up and was unable to find it at the time. Thanks.

the easiest way to get to it is from underneath the van. you can get to the cps by running your arm up beside the exhaust pipe. the nut that holds the cover on is a #10 if i remember right.the cover will have a hump in it with one nut on a stud and you should be able to see the wires from the connector going to it.they are stubborn to get out.i used a flat screwdriver and pulled just a little on the wires to get the "o" ring to pop out.when you put one back in coat the "o" ring with oil or vaseline so it will go in easier.did you ohm the tps yet?

rkvons · #21 11-01-2008, 05:07 PM

Well I just got done trying to swap MAP sensors with my other car, a 1998 Grand Prix GTP. The keying on the electric connector is different, so I was not able to do that. However, I did the LIM job on my Montana last year and while doing so, I broke my old MAP sensor. I had to go to the autoparts store and get another one. So I was thinking that that was the problem. I went up and picked up another one and put it on. Still have a problem. One thing I did though, is, I disconnected the vacuum line to the fuel pressure regulator and plugged it with a screw. I also capped the regulator vacuum port. I waited 10 minutes and tried to start it and it started right up. I then hooked it up correctly, got it running for a minute, shut it off and waited 10 minutes. When I tried to start it, it was hard to start.

rockwood84 · #22 11-03-2008, 12:14 PM

try letting the pump build up pressure by leaving the key on a couple minutes before you try to crank it.the diaphram in the regulator is probably cracked and letting the fuel pressure fall. if you build up the fuel pressure before you crank it and it starts up then put a regulator on it and it should crank up like new.

rkvons · #23 11-03-2008, 05:44 PM

First of all I want to thank you all for your help. I will not give up. I took today off and worked on her again. Here's what I did. I bought a Fuel pressure test kit and put it on. That is not the problem. The fuel pressure immediately goes up over 40 PSI when I turn the key to on. When it is running, it is around 38-39 PSI. When I turn the car off, it does not really bleed off very much, but immediately goes back up with the key on. I changed Idle Air Control Solenoids with my 1998 Grand Prix. It still has a problem. I took the Throttle Position Sensor off and measured it with an Ohm meter. I could not really get a consistant reading so I figured that was it. I went to Advance and picked up another one and put it on. Nope!

rockwood84 · #24 11-03-2008, 05:58 PM

what did the fuelpressure look like after ten minutes?

rkvons · #25 11-03-2008, 08:27 PM

Quote:

Originally Posted by rockwood84

what did the fuelpressure look like after ten minutes?

It was at about 20 PSI I suppose. It looked like it was half way to 40. It would actually go up at first when I turned it off and then start drifting down.

rkvons · #26 11-05-2008, 01:04 PM

Additional things I did. I changed the Camshaft Position Sensor ( The one under the power steering pump). Still has problem. I also bought a can of Carb. cleaner, took the Idle Air Control Module out and sprayed into the intake, sprayed the Module and sprayed into the hole where the module goes. A lot of nasty stuff was rinsed out, but the problem still remains. The wife is starting to think I am not a man anymore.

rockwood84 · #27 11-05-2008, 08:33 PM

Quote:

Originally Posted by rkvons

It was at about 20 PSI I suppose. It looked like it was half way to 40. It would actually go up at first when I turned it off and then start drifting down.

did you try seeing what the pressure was after ten minutes with the key on. if it is at twenty after ten minutes and you turn the key on does it go up to 40-50 and stay there or slowly build its way up. say 25 then 30 then 35.

rkvons · #28 11-05-2008, 08:50 PM

Quote:

Originally Posted by rockwood84

did you try seeing what the pressure was after ten minutes with the key on. if it is at twenty after ten minutes and you turn the key on does it go up to 40-50 and stay there or slowly build its way up. say 25 then 30 then 35.

When I hook up the pressure test kit and turn the key on, it bangs up to 40+ PSI immediately. I start the car and it goes down to 38-39. When I turn it off, it slowly drifts down to 20 PSI after 10 minutes. So here is what I did. I hooked the gauge on and started it and let it run for a minute. I turned it off with the key out. I watched the pressure slowly bleed away to about 20 PSI after exactly 10 minutes. I tried starting it. It was difficult to start. Hunted for idle, stalled, etc. I then got it running again and let it run for a minute. This time though, I turned the key off and immediately ran around to the front and pressed the button on the test kit to relieve the pressure in the fuel rail. I kept pressing it to make sure there was no pressure there. I then waited exactly 10 minutes and tried again and bingo, it started right up. Hmmm. One or more leaky injectors is what I'm thinking. I am running fuel system cleaner in it right now.

jester805 · #29 11-06-2008, 03:58 PM

Just got my '05 back from the second dealer. (The first one was an idiot and wouldn't do anything for me). Anyway, they told me they took the throttle body a part and it was FULL of carbon. They cleaned it out real good with a wire brush and couldn't replicate the problem after that.

They also told me that my van had an alcohol content of 12%. I didn't know what that really meant, but he said it was bad. He suggested getting gas some place that does NOT contain ethanol.

Hope that helps

JabbaTHutt · #30 11-09-2008, 07:17 AM

Ethanol is very hard on many items in the fuel system, I think they figured out that at 10% which I think it is you see on most fuel pumps, at least here in canada is a safe limit, anything over that you should be driving an E85 car. At 12% maybe is when the hoses and gaskets and aluminum parts start to break down much faster. I never thought of this before but I had to change the fuel pump in my 93 dodge and the contacts on the motor where the brushes contact where black. Eventually the new one, of course a few months after warranty ran out started to get hard to start, I was told there is a back flow valve in the fuel pump that was not working, as soon as you turned the key off the fuel would flow back to the tank, being the computer knows the engine is warm its trying to start itself as though it is warm and I would have to crank it till it bleed the air out. When it was cold it started just fine, could run it a few minutes and it would still start fine, and could do this till it got up to temp then it was back to cranking it again, who knows.

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