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Old 12-13-2018, 10:04 AM   #1
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8.1L HARD COLD START different cause

a year ago my '01 8.1L began getting longer and longer to start when engine was cold [as in hasn't been run in 6 hours]

I fixed it THAT time by replacing the crank position sensor---a known problem in 2001-2003 8.1L.........I knew it was a spark/spark timing issue because squirting raw gas down the throttle throat did not help.

THIS TIME, alluva sudden, you would have to crank it 3-4-5-6 times on cold start up only...........this time, squirting raw gas down throttle throat and it would start immediately.

A check of fuel pump pressure, pressure regulator [pressure rises alittle then falls then comes back when accelerator is 'blipped' with engine running....and NO gas coming out of vacuum hose connected to pressure regulator (regulator is on fuel rail top of engine)]..........and turn key OFF and it holds pressure falling VERY slowly means check valve is good.

a bad check valve [usually in fuel pump canister in tank]will cause hard starting when hot OR cold, tho alittle worse when cold [just went thru this with my 4.8L GM pickup.....also same truck long ago had a crack in pressure regulator diaphragm---THAT makes it hard to restart AFTER initial startup but only if it SITS for a minute to 30 minutes (over rich condition by fuel going into manifold thru vacuum hose on regulator)

I rented[for free] a loaner fuel pressure gauge from AutoZone.

sender is on passenger side with three wires going to it....accessed thru wheel well........I was able to turn old on out n new one in with an open end wrench [big wire connecter precludes socket or box wrench].....22mm

testing of the new sensor saw 3,630 OHMS between the two black leads[tho don't take this as the gospel, now that I am testing the old one and its close to same # but decimal point moved, I'm thinking I mighta messed up on that decimal point, but probly NOT] ....at 65 degrees....no resistance between any other leads.

old bad sensor saw 400 OHMS ..........

ANYWAY, MH starts cold like it used to.......almost immediately, like an injected motor should.


best price was 86$ on amazon........tho I saw it for up to $296.......Standard Motor Products TX102.....PART:


https://www.amazon.com/Standard-Moto...58412548&psc=1
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Old 12-13-2018, 11:34 AM   #2
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oooh...and amazon n ebay

will tell u its the wrong part........but they are wrong.
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Old 12-13-2018, 02:36 PM   #3
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Does that sense temperature or pressure.
It says coolant sensor so.....
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Old 12-13-2018, 03:47 PM   #4
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it senses temperature

I believe the '01 and '02 are the same 3 wire.......I think the '03+ are TWO wire......the TWO wire ones are much cheaper.

my temp gauge MAY have been acting funny [didn't drive it very far broke]

I DO know the electric cooling fans came on when the gauge said 140[they are suppose to come on at 180 I believe]
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Old 12-13-2018, 08:27 PM   #5
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I'm confused. Is this a coolant temp issue or a fuel pressure issue?

And most importantly, did the amazon coolant temp sender fix the problem?
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Old 12-14-2018, 05:49 AM   #6
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lean fuel issue from coolant temperature sensor

a coolant temperature SENSOR issue....sending incorrect engine temperature readings to the ECM.......causing a LEAN fuel trim on cold start up [sensor is SUPPOSE to tell ECM the engine is cold so ECM can lengthen fuel pulse at injector, adding fuel] .....this turned out to be the problem THIS TIME.

I CHECKED the fuel pressure, check valve and regulator because they could cause a lean mix also, tho these would be present at warm engine temps, too[but would not show up as bad], but I wanted to begin at the beginning.

I KNEW it was a fuel issue because squirting fuel down throttle made cold hard start issue disappear.

Another tip off is when finally started cold, the engine idle WAS low---500rpms.......on a cold start up the idle is SUPPOSED to be increased to 900rpms and reduced to 700 over the course of a minute or two.....this was another indication the ECM was being told by the temp sensor that the engine was WARM......when in actuality it was COLD.


Changing the sensor FIXED the problem.

a year ago, the same hard cold start issue was from a crank position sensor.....I figured that out on the fact that fuel squirts did not help issue.....AND research told me there was a KNOWN issue with '01 and '02 crank sensors.
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Old 12-14-2018, 01:10 PM   #7
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Quote:
Originally Posted by boatman10 View Post
a coolant temperature SENSOR issue....sending incorrect engine temperature readings to the ECM.......causing a LEAN fuel trim on cold start up [sensor is SUPPOSE to tell ECM the engine is cold so ECM can lengthen fuel pulse at injector, adding fuel] .....this turned out to be the problem THIS TIME.

I CHECKED the fuel pressure, check valve and regulator because they could cause a lean mix also, tho these would be present at warm engine temps, too[but would not show up as bad], but I wanted to begin at the beginning.

I KNEW it was a fuel issue because squirting fuel down throttle made cold hard start issue disappear.

Another tip off is when finally started cold, the engine idle WAS low---500rpms.......on a cold start up the idle is SUPPOSED to be increased to 900rpms and reduced to 700 over the course of a minute or two.....this was another indication the ECM was being told by the temp sensor that the engine was WARM......when in actuality it was COLD.


Changing the sensor FIXED the problem.

a year ago, the same hard cold start issue was from a crank position sensor.....I figured that out on the fact that fuel squirts did not help issue.....AND research told me there was a KNOWN issue with '01 and '02 crank sensors.
Thanks Boatman. This helps a lot.
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Old 12-15-2018, 06:21 AM   #8
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sure, man

To me, squirting fuel down the throat on a startup issue is easiest way to begin a fuel-or-spark flow chart, eh?

i damn sure don't know everything, but i'm fairly sure i know what i DO know.....and have learned some of that from YOUR posts.

AKIQPilot........thats been rolling around in my head for a coupla years now....i'm guessing AK---Alaska...thats easy..........IQ----PH.D.? ..........Pilot---got an airplane pilots ticket or captained commercial? [from the TV this florida boy thinks ya'll go to get groceries in airplanes instead of cars in Alaska]

OR the IQ---something to do with your previous Itasca RV..........Pilot-----being its driver.

howmidoin?
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Old 12-16-2018, 08:49 AM   #9
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Quote:
Originally Posted by boatman10 View Post
AKIQPilot........thats been rolling around in my head for a coupla years now....i'm guessing AK---Alaska...thats easy..........IQ----PH.D.? ..........Pilot---got an airplane pilots ticket or captained commercial? [from the TV this florida boy thinks ya'll go to get groceries in airplanes instead of cars in Alaska]

OR the IQ---something to do with your previous Itasca RV..........Pilot-----being its driver.

howmidoin?
Maybe the A-6 Intruder (mode Q)?

boatman, Did your dash temp gauge read correctly all the time? I have a similar intermittent issue on a chevy SUV. I know, just spent the $15 and swap it out, but inquiring minds want to know - mine is either a ground issue or sensor
Thanks
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Old 12-16-2018, 02:27 PM   #10
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Quote:
Originally Posted by boatman10 View Post
To me, squirting fuel down the throat on a startup issue is easiest way to begin a fuel-or-spark flow chart, eh?

i damn sure don't know everything, but i'm fairly sure i know what i DO know.....and have learned some of that from YOUR posts.

AKIQPilot........thats been rolling around in my head for a coupla years now....i'm guessing AK---Alaska...thats easy..........IQ----PH.D.? ..........Pilot---got an airplane pilots ticket or captained commercial? [from the TV this florida boy thinks ya'll go to get groceries in airplanes instead of cars in Alaska]

OR the IQ---something to do with your previous Itasca RV..........Pilot-----being its driver.

howmidoin?
Hahaha. Well, yes. AK = Alaska Pilot = Private Pilot. IQ is a long story.

I have races snowmobiles in some form or another for most of my life. In the early 2000's when webforums first kicked off I was racing for Polaris on the Polaris ProX platform. The first webforum I joined in 2001 was a snowmobile forum and I chose the logon ID of AKProXPilot. We literally flew those snowmobiles around the track. In 2005 Polaris introduced the IQ chassis sleds and we began racing them. That year I changed my LogOn ID to AKIQPilot. I pretty much use it on all of the nearly dozen webforums that I belong to.

So IQ was/is the type of snowmobile chassis that Polaris uses for their race and consumer snowmobiles.
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Old 12-16-2018, 07:32 PM   #11
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AKIQPilot

That's so cool.
And I know that you are really smart too!!

Stan
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Old 12-16-2018, 07:37 PM   #12
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When I was a First Officer (FO) I called myself the Flap Operator or the Switchflicker, cause it seemed all I was allowed to do was flick switches and put the flaps up and down.
Of course the above is an exaggeration and it's not as cool as AKIQPilot, but I try

Stan.
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Old 12-17-2018, 06:48 AM   #13
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Tomwalt

i didn't drive it far, but the gauge was reading low........... but the electric fans were coming on when the shouldn't have[both in reality AND according to the low temp reading] .....they come on with the AC on and engine temp over 180DEG i am told........so in THAT circuit the ECM thought the engine was WARMER than it was [exactly like it did on a cold start....or must have because it leaned it out]

tho the gauge read low.

theres 3 wires on sensor so theres different multiple signals generated.
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Old 12-17-2018, 08:45 AM   #14
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Thanks, looks like a $15 temp sensor is the next logical step for me.
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