Fuel tank selectrical issue

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Captain J

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Greeting
I’m new to this form and I need advice/help.
I’ve a 1987 GMC Sierra with 7.4L TBI and auto transmission, factory dual fuel tanks.
I replaced the fuel sending units on both tanks, fuel filter, fuel lines.
The issue is this, truck starts rough,
 

Charlie

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:welcome:
 

Rickf

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Was it running rough before you installed the new parts?
 

chengny

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Greeting
I’m new to this form and I need advice/help.
I’ve a 1987 GMC Sierra with 7.4L TBI and auto transmission, factory dual fuel tanks.
I replaced the fuel sending units on both tanks, fuel filter, fuel lines.
The issue is this, truck starts rough,


The issues are:
  1. truck starts rough, sometimes it quits, but once warmed up it’s ok.
  2. If I use right tank the truck is running fine, however if I select left tank, engine will quit and service engine soon will come on (code is 43).
So, if you start up on the LH tank, it never runs well - even when warmed up? And if you start up on the RH tank, it struggles at first, but then after it warms up it runs okay forever. However, while running well on the RH tank, and you switch tanks...the engine stalls?

And like Rick asks; Were all those parts replaced in an effort to remedy this condition? Or, were things going great until the parts were changed and then the trouble began? Or maybe some combination of those two scenarios?

On the DTC 43 - there's something wrong there. It is associated with the ESC (electronic spark control) system, which is a knock sensor connected directly to the ECM. Briefly, the ECM will temporarily retard ignition timing if the sensor detects engine knock.

There is only one code generated by the ESC - 43. That code indicates a low voltage signal from the knock sensor for longer than 5 seconds.

Problem is - as far as I know - the 7.4 L engine wasn't equipped with ESC until 1990. How are you reading the DTC's; with a scanner, or are you counting flashes?
 

Captain J

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Was it running rough before you installed the new parts?
Truly I never enjoyed driving it since I bought it from USA, I saw a video of it running fine, when I received it, it will start however fuel will flood the cancter in front, so I checked the fuel tank, fuel filter and fuel sending units all were rusted. So I replaced them with Spectra fuel tanks, fuel sending units and Durlast fuel filter, replaced injectors with new GM injectors,
 

Captain J

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The issues are:
  1. truck starts rough, sometimes it quits, but once warmed up it’s ok.
  2. If I use right tank the truck is running fine, however if I select left tank, engine will quit and service engine soon will come on (code is 43).
So, if you start up on the LH tank, it never runs well - even when warmed up? And if you start up on the RH tank, it struggles at first, but then after it warms up it runs okay forever. However, while running well on the RH tank, and you switch tanks...the engine stalls?
It used to start fine when I got the truck, But it had issues, can’t select fuel tank, more info in the second answer.
Now it won’t start on LH tank, it will crank but no start.
If I select RH tank it will start, but engine will riv up and riv down, sometimes it quits, but otherwise after warming up it’s fine. and yes if truck is running and switch to LH it will quite and service engine soon will come on.


And like Rick asks; Were all those parts replaced in an effort to remedy this condition? Or, were things going great until the parts were changed and then the trouble began? Or maybe some combination of those two scenarios?
As I told Rick, I bought this truck from US, import it to Qatar, had issue starting, and fuel selector electric issues, it won’t switch between tanks, in addition fuel will flood engine at the canister. Fuel tank, fuel filter, fuel sending units were all rusted out.

On the DTC 43 - there's something wrong there. It is associated with the ESC (electronic spark control) system, which is a knock sensor connected directly to the ECM. Briefly, the ECM will temporarily retard ignition timing if the sensor detects engine knock.
I am not sure, I need a picture illustration to know it, or the location of ESC.

There is only one code generated by the ESC - 43. That code indicates a low voltage signal from the knock sensor for longer than 5 seconds.

Problem is - as far as I know - the 7.4 L engine wasn't equipped with ESC until 1990. How are you reading the DTC's; with a scanner, or are you counting flashes?
Counting flashing after I connected paper clip to DTC.
 

chengny

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The issues are:
  1. truck starts rough, sometimes it quits, but once warmed up it’s ok.
  2. If I use right tank the truck is running fine, however if I select left tank, engine will quit and service engine soon will come on (code is 43).
So, if you start up on the LH tank, it never runs well - even when warmed up? And if you start up on the RH tank, it struggles at first, but then after it warms up it runs okay forever. However, while running well on the RH tank, and you switch tanks...the engine stalls?
It used to start fine when I got the truck, But it had issues, can’t select fuel tank, more info in the second answer.
Now it won’t start on LH tank, it will crank but no start.
If I select RH tank it will start, but engine will riv up and riv down, sometimes it quits, but otherwise after warming up it’s fine. and yes if truck is running and switch to LH it will quite and service engine soon will come on.


And like Rick asks; Were all those parts replaced in an effort to remedy this condition? Or, were things going great until the parts were changed and then the trouble began? Or maybe some combination of those two scenarios?
As I told Rick, I bought this truck from US, import it to Qatar, had issue starting, and fuel selector electric issues, it won’t switch between tanks, in addition fuel will flood engine at the canister. Fuel tank, fuel filter, fuel sending units were all rusted out.

On the DTC 43 - there's something wrong there. It is associated with the ESC (electronic spark control) system, which is a knock sensor connected directly to the ECM. Briefly, the ECM will temporarily retard ignition timing if the sensor detects engine knock.
I am not sure, I need a picture illustration to know it, or the location of ESC.

There is only one code generated by the ESC - 43. That code indicates a low voltage signal from the knock sensor for longer than 5 seconds.

Problem is - as far as I know - the 7.4 L engine wasn't equipped with ESC until 1990. How are you reading the DTC's; with a scanner, or are you counting flashes?


As things stand now:

1. Is fuel still entering and flooding the evap canister? Does it actually fill up to the point that gas comes out of the air inlet?

2. Are you currently able to switch consistently between L & R tanks?

3. Is the truck driveable - or is all this happening with it parked and at idle?


You shouldn't have an ESC system on that truck - so you shouldn't be throwing a code 43. But if you want to be sure, check whether the two components shown below are installed. The dwg is from the 1990 Service Manual. I couldn't use your model year because, AFAIK, 90 was the first year that the 454 engine used the ESC system. So there is no mention of it in the 87 book:

You must be registered for see images attach
 

Captain J

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The issues are:
  1. truck starts rough, sometimes it quits, but once warmed up it’s ok.
  2. If I use right tank the truck is running fine, however if I select left tank, engine will quit and service engine soon will come on (code is 43).
So, if you start up on the LH tank, it never runs well - even when warmed up? And if you start up on the RH tank, it struggles at first, but then after it warms up it runs okay forever. However, while running well on the RH tank, and you switch tanks...the engine stalls?
It used to start fine when I got the truck, But it had issues, can’t select fuel tank, more info in the second answer.
Now it won’t start on LH tank, it will crank but no start.
If I select RH tank it will start, but engine will riv up and riv down, sometimes it quits, but otherwise after warming up it’s fine. and yes if truck is running and switch to LH it will quite and service engine soon will come on.


And like Rick asks; Were all those parts replaced in an effort to remedy this condition? Or, were things going great until the parts were changed and then the trouble began? Or maybe some combination of those two scenarios?
As I told Rick, I bought this truck from US, import it to Qatar, had issue starting, and fuel selector electric issues, it won’t switch between tanks, in addition fuel will flood engine at the canister. Fuel tank, fuel filter, fuel sending units were all rusted out.

On the DTC 43 - there's something wrong there. It is associated with the ESC (electronic spark control) system, which is a knock sensor connected directly to the ECM. Briefly, the ECM will temporarily retard ignition timing if the sensor detects engine knock.
I am not sure, I need a picture illustration to know it, or the location of ESC.

There is only one code generated by the ESC - 43. That code indicates a low voltage signal from the knock sensor for longer than 5 seconds.

Problem is - as far as I know - the 7.4 L engine wasn't equipped with ESC until 1990. How are you reading the DTC's; with a scanner, or are you counting flashes?


As things stand now:
Let me say I truly appreciate your help and feedback.

1. Is fuel still entering and flooding the evap canister? Does it actually fill up to the point that gas comes out of the air inlet?
No, it was fixed.

2. Are you currently able to switch consistently between L & R tanks?
Yes I can, however switching to L tank engine will quit & service engine soon comes on.
3. Is the truck driveable - or is all this happening with it parked and at idle?
As I mentioned, 1st start of the day, truck will start (engine will rev up and down, if cold it will quit, but once warm it’s fine). Subsequent starts are fine.
Yes it’s drivable using R tank with no issues.



You shouldn't have an ESC system on that truck - so you shouldn't be throwing a code 43. But if you want to be sure, check whether the two components shown below are installed. The dwg is from the 1990 Service Manual. I couldn't use your model year because, AFAIK, 90 was the first year that the 454 engine used the ESC system. So there is no mention of it in the 87 book:
I’ll check. Thanks
You must be registered for see images attach
 

Captain J

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Juday Hajri
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1972, 1986, 1987, 1997, 2013
Truck Model
C/K 2500, R3500, 2500HD
Engine Size
5.7, 7.4, LS, 6.0
The issues are:
  1. truck starts rough, sometimes it quits, but once warmed up it’s ok.
  2. If I use right tank the truck is running fine, however if I select left tank, engine will quit and service engine soon will come on (code is 43).
So, if you start up on the LH tank, it never runs well - even when warmed up? And if you start up on the RH tank, it struggles at first, but then after it warms up it runs okay forever. However, while running well on the RH tank, and you switch tanks...the engine stalls?
It used to start fine when I got the truck, But it had issues, can’t select fuel tank, more info in the second answer.
Now it won’t start on LH tank, it will crank but no start.
If I select RH tank it will start, but engine will riv up and riv down, sometimes it quits, but otherwise after warming up it’s fine. and yes if truck is running and switch to LH it will quite and service engine soon will come on.


And like Rick asks; Were all those parts replaced in an effort to remedy this condition? Or, were things going great until the parts were changed and then the trouble began? Or maybe some combination of those two scenarios?
As I told Rick, I bought this truck from US, import it to Qatar, had issue starting, and fuel selector electric issues, it won’t switch between tanks, in addition fuel will flood engine at the canister. Fuel tank, fuel filter, fuel sending units were all rusted out.

On the DTC 43 - there's something wrong there. It is associated with the ESC (electronic spark control) system, which is a knock sensor connected directly to the ECM. Briefly, the ECM will temporarily retard ignition timing if the sensor detects engine knock.
I am not sure, I need a picture illustration to know it, or the location of ESC.

There is only one code generated by the ESC - 43. That code indicates a low voltage signal from the knock sensor for longer than 5 seconds.

Problem is - as far as I know - the 7.4 L engine wasn't equipped with ESC until 1990. How are you reading the DTC's; with a scanner, or are you counting flashes?


As things stand now:

1. Is fuel still entering and flooding the evap canister? Does it actually fill up to the point that gas comes out of the air inlet?

2. Are you currently able to switch consistently between L & R tanks?

3. Is the truck driveable - or is all this happening with it parked and at idle?


You shouldn't have an ESC system on that truck - so you shouldn't be throwing a code 43. But if you want to be sure, check whether the two components shown below are installed. The dwg is from the 1990 Service Manual. I couldn't use your model year because, AFAIK, 90 was the first year that the 454 engine used the ESC system. So there is no mention of it in the 87 book:

You must be registered for see images attach
I just checked the engine to see if it has the ESC knock sensor & ESC hybrid function as shown in the illustration, there are none.
 

Captain J

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Juday Hajri
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1972, 1986, 1987, 1997, 2013
Truck Model
C/K 2500, R3500, 2500HD
Engine Size
5.7, 7.4, LS, 6.0
Was it running rough before you installed the new parts?
No, it was fine.
I installed the most of the parts, fuel tanks, fuel filter, fuel sending units, hoses, fuel injectors.
Tanks, fuel sending units were all rusted out, fuel filter was clogged.

The truck was in a garage for overhauling the engine, the crank shaft was slightly damaged due to oil pump failure.
 

Captain J

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Anyone,
 

Captain J

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C/K 2500, R3500, 2500HD
Engine Size
5.7, 7.4, LS, 6.0
Hello
I just uploaded a video on my YouTube channel.
You can see that engine starting on the Right tank, you can hear engine sound. When switching to LH tank engine quits. Also showing service engine soon
Waiting for your reply

xc_hide_links_from_guests_guests_error_hide_media
 

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