Fuel pump wiring help

[PeterH-350LE]

Originally Posted by 92landyacht

Might want to try here:

https://www.stockwiseauto.com/acdelc...olet&Model=P30

or here:

http://oemcats.com/oem-parts/10052973.html

zero in stock and if you follow some of the links you may be directed to fraudulent websites, that claim to have it and will charge you for it and never ship. I went through that with a speedometer.

[92landyacht]

Originally Posted by PeterH-350LE

zero in stock and if you follow some of the links you may be directed to fraudulent websites, that claim to have it and will charge you for it and never ship. I went through that with a speedometer.

Well, there's always the after market option:

https://www.opgi.com/air-fuel-delive...RoCFYYQAvD_BwE

or

https://www.amazon.com/Revolution-El.../dp/B00BNZ05JM

or

https://www.ebay.com/itm/33359269580...RoC5DMQAvD_BwE

[PeterH-350LE]

Originally Posted by 92landyacht

Well, there's always the after market option:

https://www.opgi.com/air-fuel-delive...RoCFYYQAvD_BwE

or

https://www.amazon.com/Revolution-El.../dp/B00BNZ05JM

or

https://www.ebay.com/itm/33359269580...RoC5DMQAvD_BwE

nope, the function of those controllers is already taken care of by the PCM/ECU. The module in question extends the "priming" from 2-3 seconds to ~25 secs to eliminate hot start problems.

What type of fuel system does your 92 Landyacht have. I would think you have the same Throttle body TBI220 and should have the very same components?

[92landyacht]

Yep, same TBI 454 but I don't seem to have anything more than the ECM 3 second delay. After a while of sitting I have to turn the ignition on a couple of times before it will start right. After that it's just fine. Only happens if it's been sitting for a month or more.

Might add something to make it easier. My advantage is that I can design one for myself as I have both the hardware and software knowledge. Might be a fun project actually. Wouldn't take much to switch the pump on and wait 20 seconds. Just looking at t he board in the pics posted it actually a pretty simple device. If someone sent ma a bad one I'm very sure I could reproduce it.

[PeterH-350LE]

Originally Posted by 92landyacht

Yep, same TBI 454 but I don't seem to have anything more than the ECM 3 second delay. After a while of sitting I have to turn the ignition on a couple of times before it will start right. After that it's just fine. Only happens if it's been sitting for a month or more.

Might add something to make it easier. My advantage is that I can design one for myself as I have both the hardware and software knowledge. Might be a fun project actually. Wouldn't take much to switch the pump on and wait 20 seconds. Just looking at t he board in the pics posted it actually a pretty simple device. If someone sent ma a bad one I'm very sure I could reproduce it.

Interesting, you may want to check pin 490 on your ACDL (ODB-1). It will show you the voltage to the fuel pump from the hot start Module. Its the upper left pin. With the new working one, its shows voltage for ~30 secs with ignition on. Nothing in run

You probably do have the module, but it quit working. Its hidden behind the ECU way deep under the dash. I have to lay with my head on the floor and look to the left of the steering column.
If you send me your address via pm, I can send you my old module. Would be happy to pay you for a spare. I am spare parts junkie.

[92landyacht]

If you have a bad module I'll take you up on that offer. Sounds like a fun project and I'm always looking for a fun, mentally stimulating, project.

I did find these threads to help with the project:

http://67-72chevytrucks.com/vboard/s...d.php?t=429691

https://www.gm-trucks.com/forums/top...l-pump-module/

https://chevroletforum.com/forum/exp...burning-84071/

Together they pretty much spell out how things are wired together and how the system works.

[PeterH-350LE]

Originally Posted by 92landyacht

If you have a bad module I'll take you up on that offer. Sounds like a fun project and I'm always looking for a fun, mentally stimulating, project.

I did find these threads to help with the project:

http://67-72chevytrucks.com/vboard/s...d.php?t=429691

https://www.gm-trucks.com/forums/top...l-pump-module/

https://chevroletforum.com/forum/exp...burning-84071/

Together they pretty much spell out how things are wired together and how the system works.

yup, that covers it, easy to understand once you know what to understand and where they hid it.
from one of your links:



>>>>>>Realize it's an old thread, but I've read that the hot fuel module was also added to lighter trucks that were equipped with the big block. With either the big block or heavy towing, underhood temps were enough to cause vapor lock. Hence the extended fuel pump run time.

I think this was GM's way of a work around. They could have coded the computer to keep the fuel pump on longer in the v30's and big blocks, but it would have meant stocking a larger selection of computers. This was the cheaper solution, since the engine computer didn't care whether the engine was in a v30 or not.<<<<<

[92landyacht]

Received the damaged module from Peter a few days ago. Checked out the board and found the large transistor driver that powers the fuel pump to be burnt out and shorted. Removed the part and found the remaining circuitry was still operational. I'm now in the process of identifying all components and creating a schematic diagram of the PCB inside the module. So far I've only found a couple of parts (1 diode and 1 transistor) that I haven't found a direct match for using the identifying marks but still shouldn't be a problem as this design wasn't rocket science. For what it's worth, I found the actual fuel pump turn on on time to be about 20 seconds after power is applied. After which the module turns off and stays off until power is cycled again.

From what I've seen so far, it might actually be easier to create a new circuit design using more updated parts (voltage regulator, CPU, MOSFET driver and MOSFET switch) as these components are easier to find and cost less overall. If all works out, I'll have the original unit repaired and a new board laid out using the updated design over the next few weeks. Once I bench test it, I can verify it using my 1992 LY as a test subject.

[PeterH-350LE]

Originally Posted by 92landyacht

Received the damaged module from Peter a few days ago. Checked out the board and found the large transistor driver that powers the fuel pump to be burnt out and shorted. Removed the part and found the remaining circuitry was still operational. I'm now in the process of identifying all components and creating a schematic diagram of the PCB inside the module. So far I've only found a couple of parts (1 diode and 1 transistor) that I haven't found a direct match for using the identifying marks but still shouldn't be a problem as this design wasn't rocket science. For what it's worth, I found the actual fuel pump turn on on time to be about 20 seconds after power is applied. After which the module turns off and stays off until power is cycled again.

From what I've seen so far, it might actually be easier to create a new circuit design using more updated parts (voltage regulator, CPU, MOSFET driver and MOSFET switch) as these components are easier to find and cost less overall. If all works out, I'll have the original unit repaired and a new board laid out using the updated design over the next few weeks. Once I bench test it, I can verify it using my 1992 LY as a test subject.

Julius, thats awesome. I wished I had your skill set on this subject. Have you figured out the lower then system voltage when the module is engaged? You said using your 1992 LY as a test subject, does that mean you found the module on your set up?

[92landyacht]

Originally Posted by PeterH-350LE

Julius, thats awesome. I wished I had your skill set on this subject. Have you figured out the lower then system voltage when the module is engaged? You said using your 1992 LY as a test subject, does that mean you found the module on your set up?

Nope, haven't found mine yet, but haven't really looked for it either. Can you give me a clue as to where exactly to look for it? I understand that it's left of the steering column bit is that left while on your back or looking straight on? How high up is it? Is it mounted to anything or just hanging?

Seems like mine must be bad or missing since I don't have the 20 second pump running after ignition turn on. Every time I start the RV after it's sat for a while, I have to turn the ignition on and off a couple of times to get it to start right away. If I just turn the key on to start it, it takes a bit of cranking before it finally starts. This only happens if it has sat for over a month or more between starts. Once it starts, it will continue to start reliably unless it sits again.

[PeterH-350LE]

Originally Posted by 92landyacht

Nope, haven't found mine yet, but haven't really looked for it either. Can you give me a clue as to where exactly to look for it? I understand that it's left of the steering column bit is that left while on your back or looking straight on? How high up is it? Is it mounted to anything or just hanging?

Seems like mine must be bad or missing since I don't have the 20 second pump running after ignition turn on. Every time I start the RV after it's sat for a while, I have to turn the ignition on and off a couple of times to get it to start right away. If I just turn the key on to start it, it takes a bit of cranking before it finally starts. This only happens if it has sat for over a month or more between starts. Once it starts, it will continue to start reliably unless it sits again.

Assuming it is in the same location as mine, with your head on the floor looking to the left of the Steering column, you should see the ECM with 2 big connectors coming out of the left end of the unit. the ECM is actually mounted inside of a small enclose that holds the ECM with 3 almost unreachable screws.. try to reach just forward of the ECM/enclosure and see if it still is mounted with a clip to the forward side of the ECM enclosure. Looking down from the removed dash didn't show it in my case. You now have my old unit to see what it looks like.

[bkahler]

In other words, you need to be a contortionist to access it....

[92landyacht]

OK, I'll take a look to see if I can locate mine. Too bad I didn't do this a few weeks ago... at that time I had the front driver's and passenger's seats removed in order to install new seats. Basically I had the entire floor to lay down on.

I'll let you know if I find it and what condition it's in. Might be easier to locate then yours since the ECU was removed by a truck repair company a couple of years ago in order to replace it. Maybe they just left the hot start module hanging.

[PeterH-350LE]

Originally Posted by 92landyacht

OK, I'll take a look to see if I can locate mine. Too bad I didn't do this a few weeks ago... at that time I had the front driver's and passenger's seats removed in order to install new seats. Basically I had the entire floor to lay down on.

I'll let you know if I find it and what condition it's in. Might be easier to locate then yours since the ECU was removed by a truck repair company a couple of years ago in order to replace it. Maybe they just left the hot start module hanging.

or they removed it. Not having it there, is better than feeding the low 10V to the fuel pump with ignition on, as it was in my case. Besides it burning out the fuel pump eventually, it also did over write the oil pressure switch safety signal.

[92landyacht]

Originally Posted by PeterH-350LE

or they removed it. Not having it there, is better than feeding the low 10V to the fuel pump with ignition on, as it was in my case. Besides it burning out the fuel pump eventually, it also did over write the oil pressure switch safety signal.

I don't think that the shop removed it, if it is missing, since the RV never had the 20 second prime function since I purchased it ~10 years ago. As for the overriding of the oil pressure switch, that was always part of the design implementation. Although, in your case, it was not supposed to do it after the 20 second prime was completed. Since yours was shorted (Emitter to Collector) the switch was always on beyond the 20 seconds while the ignition is on. How the output transistor fails is a luck of the draw. Some will go open and some will short. Just depends on what breaks down first.

As for the 10V output, that may be normal since they used a PNP transistor as a switch and there is significant voltage loss through it. As you noted, the replacement unit did the same. The higher the current through the module, the greater the voltage loss will be.

One of the reasons I'm considering replacing the output transistor with a N-Channel MOSFET is for the lower internal resistance when switched on. I could use a simple relay as well, but one of the design constraints is that the board would have to fit into the existing housing. Since the housing is relatively thin, finding a relay that could fit into the original box and be able to provide the needed 10 amps to the fuel pump would be difficult.

Still investigating viable designs so not sure what the final implementation will be.

[92landyacht]

Decided to start a new thread since this project will take on its own life.