73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: kjnmontana on June 21, 2020, 07:13:51 PM
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The current location of the fuel tank selector valve on my 89 dual tank V3500 former tow truck is incredibly hard to access and replace. I have a ton of room behind the cab bench seat to install the valve and route the fuel lines from each tank forward to the mechanical fuel pump using flexible fuel hosing. I’m looking for feedback on why this should or should not be a doable thing. Thanks
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In line with this thread, the current location of the fuel tank selector valve on my 89 dual tank V3500 former tow truck is incredibly hard to access and replace. I have a ton of room behind the cab bench seat to install the valve and route the fuel lines from each tank forward to the mechanical fuel pump using flexible fuel hosing. I’m looking for feedback on why this should or should not be a doable thing. Thanks
It sounds like you’re talking about relocating the selector valve itself inside the cab. If this is what you’re thinking, I think it would be an unwise choice. I would try to find somewhere - anywhere - other than in the cab.
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Thanks for the reply, that’s my problem, a short bed with saddle tanks, mufflers and box cross members makes it hard to find a protected, accessible, not exposed to exhaust heat location, thus the cab, which in my Mad Max thinking, could be an option, as it would be protected and if properly plumbed, reasonably safe. The original location was insane and probably the reason the previous owner bypassed it and only used one direct feed tank.
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You hit the nail squarely on its head with your Mad Max reference. LOL
Fuel lines should never be routed above or into/through a passenger compartment or enclosed storage area under any circumstances. The potential for hazardous leaks, fuel vapor accumulation, occupant exposure to toxic vapors, and fire make the "convenience" of relocating the selector valve inside the cab exceedingly risky and jeopardizes the safe operation of a vehicle. In addition, a modification of that nature might nulify insurance coverage in the event of a fire, not to mention, the question of legality; it certainly is illegal with regard to buses.
Replacing a fuel selector valve mounted in its factory location inside the right frame rail is a trying nuisance the first time through, but certainly is doable, as many thousands of people can attest. I've replaced dozens of valves. Not fun but achievable and easier with each replacement.
1989 Service Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/X8932_1989_GMC_RVGP_Light_Duty_Truck_Service_Manual.pdf#page=911)
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Not to mention personal liability if anything ever were to happen to an occupant as a result of your "modification"
Yeah they're a pain to service but luckily don't require frequent service.
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Thanks for the replies folks, they’re the reason I joined this group as I can talk myself into anything!
I’ve also got a post regarding wiring harnesses that if you’ve the time to comment it would be appreciated.
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BD, thanks for the digital manual, priceless.
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Thanks for the reply, that’s my problem, a short bed with saddle tanks, mufflers and box cross members makes it hard to find a protected, accessible, not exposed to exhaust heat location...
If you are worried about exposure to exhaust heat, you might consider fashioning a heat shield from a piece of sheet metal that could be placed between the valve and the heat source (my ‘87’s valve has a protective shield over it from the factory). You could fashion something similar, and line it with header wrap so that heat would no longer present an issue. Such a shield would also protect the valve from rocks and road debris.
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Thanks Bake, I’ll need to trade my meat hooks in for raccoon paws...the original installation is tight to say the least.
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After laying on my shop floor under my 1989 V3500 for a few days I’ve realized swapping the valve block is not as imposing as I thought.
I do have a few questions that I hope folks can guide me on.
Background: 1989 V3500, carbureted big block with a mechanical fuel pump.
I’m replacing the RH saddle tank, both sending units, valve block and transfer switch.
My understanding is that the fuel tank transfer switch needed with a carbureted motor is the “Depress Fully” switch vice the toggle, is this correct?
My other question is with regard to the NL2 dual tank system and the use of a sub-harness that plugs into the RH tank sender wire on the RH frame rail with power coming from the fuse panel under the dash.
Is there an illustration of what the sub-harness looks like and how it is wired?
It appears I have the molded pin connector wired into the fuel gauge wire, but the other end was cut from wherever it was suppose end, so I’m not clear on how that should rewired.
Appreciated any direction.
KJ
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This thread was going so nicely...Why did you have to geek out?
The real problem is your truck us 'too new'...check the URL ::)
I'm sure someone will come to your aid, I got nothin... ???
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Yep, wasn’t sure how 73-87 url would work for me, but it’s the closet resource, and frankly it appears to be pretty close to what I’m dealing with on my truck.
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You'll find plenty of love here 8)
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My understanding is that the fuel tank transfer switch needed with a carbureted motor is the “Depress Fully” switch vice the toggle, is this correct?
My other question is with regard to the NL2 dual tank system and the use of a sub-harness that plugs into the RH tank sender wire on the RH frame rail with power coming from the fuse panel under the dash.
Is there an illustration of what the sub-harness looks like and how it is wired?
The "DEPRESS FULLY" switch was for pre-87 models. You need an AC Delco D7089C selector switch.
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=38113.0;attach=51975;image)
The NL2 sub-harness is represented by the colored lines within the red outline in the image below. On a single-tank system, pink circuit 30 that runs rearward along the right framerail from the bulkhead connector would attach directly to the left (production) fuel tank. On the dual-tank system, circuit 30 plugs into the NL2 sub-harness as shown in the diagram.
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What switch is on your truck now? Depress Fully should be the right one for carbureted models.
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The switch that was in the truck was a “Depress Fully” which I thought was the carbureted version and I’ve read where the AC Delco D7089C is for the TBI...?
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Carbureted should be Delco D7003 or Standard DS293 which is Depress Fully
TBI Should be Delco D7089C or Standard DS1807
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Two diagrams below. First is TBI, second is Carbureted.
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The depress fully which I assumed was for carbureted meanwhile I’m seeing some amazon switch reviews saying the ac delco d7089c is for TBI...?
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Vile, thanks much to you and BD...the education continues
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Carbureted should be Delco D7003 or Standard DS293 which is Depress Fully
TBI Should be Delco D7089C or Standard DS1807
This ^^^^^.
I am trying to determine what the actual differences are between the two switches besides the keying (polarization) of the connectors and the fact that the "Depress Fully" switch is momentary contact. More on this if/when information becomes available.
In the meantime, it sounds like you have the correct switch.
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Guys, can anyone explain the logic of the molded pin connector in the fuel gauge wire near the fuel block valve that Hatzie depicts in his Dual Tank Theory post?
I’m absorbing the schematics provided above and trying to understand how this connector should be incorporated into the fuel block valve wiring harness and Fuse 30 on the engine compartment fuse block.
Thanks
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(http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=1782911&stc=1&d=1525801924)
Do you mean this ^^^^^?
The pink wire pictured is circuit 30 coming directly from the fuel gauge. On a single tank system, Ckt 30 routes directly to the production tank. On a dual-tank system, it routes to the selector valve; the selector valve switches the dash gauge (Ckt 30) between tanks.
Don't confuse Ckt 30 with Ckt 139 (also a pink wire), which does connect to the fuse box.
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Got it, curious as to why a molded pin connector is required vice a straight wire from the fuel valve to circuit 30 via the wire harness?
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Dual fuel tanks are an add-on option from the factory. It is simpler and less costly to add the NL2 harness to the existing single tank production wiring.
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Hey guys, I’m looking at the Pollak two tank motorized fuel selector valve installation sheet and I’ll be giggered if the main and aux tank leads from the wiring harness are the reverse of what your schematics...?