LT-1 issue - Page 4

John Nechiporchik · 04-13-2015, 08:29 PM

Thanks Alan. That is on the agenda.

John Nechiporchik · 04-14-2015, 11:45 AM

Following up on Alan's advise to track down the voltage loss at the TPS, I contacted a guy that Accel advised as a service rep for their product. I spoke to him several time last year when I was experiencing a no start condition and he was helpful
As I explained my low voltage to the TPS, he suggested unplugging the MAP sensor (which was getting a 5v input) and then checking the TPS input. Well, with both connectors disconnected (TPS and MAP), both input voltages from the ECM read 4.97 volts. When I installed the MAP sensor connector, the voltage to the TPS dropped back to 4.24V.
I checked the ECM ground which is directly to the battery and the ground from the rear of the cyl. head and all were clean and tight.
Would a defective MAP sensor cause excessive current draw and subsequently weaken the TPS input?? Not certain how that stuff works. The accel guy indicated the two circuits , although different pins in the ECM connector, have the same voltage reference source.
He indicated a ground problem or possibly a bad MAP sensor.

All input/experience appreciated.

John

John Nechiporchik · 04-14-2015, 01:13 PM

Update: The above tests were run with the battery at 17V.

Here's a matrix to clarify test results:

Both connectors attached: 3.75V TPS 3.75V MAP

TPS connected/MAP disconnected: 5.0V TPS 5.0V MAP

TPS disconnected/MAP connected: 4.2V TPS 4.2V MAP

Both disconnected : 5.0V TPS 5.0V MAP

Hopefully someone can make some sense out of this. The MAP sensor appears to be having the negative influence on the system.
Help!!

Thanks,

John

Ed Wright · 04-14-2015, 04:32 PM

Simply substitute another MAP sensor and re-test.

Alan Roehrich · 04-14-2015, 06:09 PM

John,
Do you have some sort of step down transformer/transistor reducing the voltage to your ECU to somewhere around 13.5 vdc, or is it happy with being supplied with 17 vdc? The reason I ask is that some ECU's do not like excessive voltage, and their internal regulators are not designed to deal with more than 14 vdc or so.

John Nechiporchik · 04-14-2015, 06:48 PM

Alan, The ECU is seeing direct voltage from 16volt battery.....typically 16.8 - 17 volts.
This set-up was in the car when I got it. The Accel support guy and I did not discuss this...but I will follow up and ask him.

John

John Nechiporchik · 04-14-2015, 09:22 PM

Installed new MAP sensor and the previous voltage of 3.75 dropped to 1.54 volts at the input side on both the MAP and TPS connectors.
For info purposes, I measured the resistance between the B and C terminals (volts in /signal out) on both MAP sensors with the following result:
Old sensor : 343
New sensor: 24 (is this a reject?) INFO CORRECTED FROM ORIGINAL POST. Had the numbers switched

Anyone have a reference number for this resistance??
Thanks,

John

Dave Noll · 04-15-2015, 02:44 AM

Quote:

Originally Posted by John Nechiporchik

Re-terminated 3 TPS leads .

Umm ..... just a thought. The wire's didn't get mixed up did they ?

John Nechiporchik · 04-15-2015, 06:34 AM

No they did not,

Kirk Morgan · 04-15-2015, 07:40 AM

When MAP sensors were common place and needed replacement we went with OEM. I had quit a few MAP and ECT sensors that weren't even close to specs. Like Ed said you need a good DVO meter to check for some problems. I use a Fluke 88 I have had for about 20 years. Not all MAP sensors have the same BAR specs as the vacume changes.

Kirk

04-13-2015, 08:29 PM	#31
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue Thanks Alan. That is on the agenda.

04-14-2015, 11:45 AM	#32
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue Following up on Alan's advise to track down the voltage loss at the TPS, I contacted a guy that Accel advised as a service rep for their product. I spoke to him several time last year when I was experiencing a no start condition and he was helpful As I explained my low voltage to the TPS, he suggested unplugging the MAP sensor (which was getting a 5v input) and then checking the TPS input. Well, with both connectors disconnected (TPS and MAP), both input voltages from the ECM read 4.97 volts. When I installed the MAP sensor connector, the voltage to the TPS dropped back to 4.24V. I checked the ECM ground which is directly to the battery and the ground from the rear of the cyl. head and all were clean and tight. Would a defective MAP sensor cause excessive current draw and subsequently weaken the TPS input?? Not certain how that stuff works. The accel guy indicated the two circuits , although different pins in the ECM connector, have the same voltage reference source. He indicated a ground problem or possibly a bad MAP sensor. All input/experience appreciated. John

04-14-2015, 01:13 PM	#33
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue Update: The above tests were run with the battery at 17V. Here's a matrix to clarify test results: Both connectors attached: 3.75V TPS 3.75V MAP TPS connected/MAP disconnected: 5.0V TPS 5.0V MAP TPS disconnected/MAP connected: 4.2V TPS 4.2V MAP Both disconnected : 5.0V TPS 5.0V MAP Hopefully someone can make some sense out of this. The MAP sensor appears to be having the negative influence on the system. Help!! Thanks, John Last edited by John Nechiporchik; 04-14-2015 at 04:28 PM. Reason: more info

04-14-2015, 04:32 PM	#34
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: LT-1 issue Simply substitute another MAP sensor and re-test. __________________ Ed Wright 4156 SS/JA

04-14-2015, 06:09 PM	#35
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,115 Likes: 1,572 Liked 1,829 Times in 414 Posts	Re: LT-1 issue John, Do you have some sort of step down transformer/transistor reducing the voltage to your ECU to somewhere around 13.5 vdc, or is it happy with being supplied with 17 vdc? The reason I ask is that some ECU's do not like excessive voltage, and their internal regulators are not designed to deal with more than 14 vdc or so. __________________ Alan Roehrich 212A G/S

04-14-2015, 06:48 PM	#36
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue Alan, The ECU is seeing direct voltage from 16volt battery.....typically 16.8 - 17 volts. This set-up was in the car when I got it. The Accel support guy and I did not discuss this...but I will follow up and ask him. John Last edited by John Nechiporchik; 04-14-2015 at 06:51 PM. Reason: more info

04-14-2015, 09:22 PM	#37
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue Installed new MAP sensor and the previous voltage of 3.75 dropped to 1.54 volts at the input side on both the MAP and TPS connectors. For info purposes, I measured the resistance between the B and C terminals (volts in /signal out) on both MAP sensors with the following result: Old sensor : 343 New sensor: 24 (is this a reject?) INFO CORRECTED FROM ORIGINAL POST. Had the numbers switched Anyone have a reference number for this resistance?? Thanks, John Last edited by John Nechiporchik; 04-15-2015 at 08:14 AM. Reason: correction

04-15-2015, 06:34 AM	#39
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue No they did not,

04-15-2015, 07:40 AM	#40
Kirk Morgan Member Join Date: Jan 2009 Posts: 230 Likes: 1 Liked 80 Times in 44 Posts	Re: LT-1 issue When MAP sensors were common place and needed replacement we went with OEM. I had quit a few MAP and ECT sensors that weren't even close to specs. Like Ed said you need a good DVO meter to check for some problems. I use a Fluke 88 I have had for about 20 years. Not all MAP sensors have the same BAR specs as the vacume changes. Kirk