Omitting intank fuel pump

[DaveVA78Chieftain]

Your welcome.  Be sure to read the Emissions Section also for the venting system information.  You will also find a drawing that shows the location of the elusive fuel pump relay on pdf page 197.

Dave

[Stripe]

So what you guys are saying, is that I would do well to have a backup electric pump? Or assisting pump? What PSI would I want?

[Rickf1985]

The carburetor wants 5-7 lbs. No more than that. The stocker uses a regulator to bring the pressure down to that level.

[DaveVA78Chieftain]

Fredrick
You haven't downloaded the Chevy MH Chassis Service Guide yet (free)?  All the info is in there (pdf page 135) on how to add an electric pump on a P30 chassis.  They recommend the Holley 12-801 pump.  You also have to regulate it down to 5-7 PSI.

Dave

[Stripe]

Oddly enough, I have. It's been on desktop for forever..  W% Just had't read through it yet.. 

[legomybago]

We just put the Holley 12-801 with the by-pass check valve I purchased from Froggy. We didn't put a regulator on because the pressure on those is 5-7, and it's mounted clear back on the rig, with a manual off/on switch on the dash...

So the maiden voyage with this set up was last weekend, he ran with just the mechanical pump on the engine (electric off)...it climbed every mountain pass from here to the coast great, (pulling a toad too) the set up weighs 15k, but it did vapor lock twice. 1) After a fuel fill up. 2) Sitting at a stop light on an off ramp of I-5. He turned the switch on for the electric pump immediatly, and BAM!! Back in business...

We think the problem maybe the 10% ethanol in the fuel now??....We didnt have this problem 2 years ago....They are trying for 15% now!!! Before anyone says B.S. on this theory!!, I need to fill the rig with non-ethanol premium, and go for a trip...I think when I go to the coast myself with it pretty soon I will do that and see how it performs.. Hm?

[Stripe]

If you look at the PDF file Dave and I are talking about and read the section Dave points out, there is a statement in there about oil companies (illegally I might add) not listing that their fuel has alcohol (they called it Gasahol back then) mixed into it.  Here is a short excerpt...


"Fuel Properties
As part of the investigation, Chevrolet Fuel and Lubrication Engineers conducted a nationwide survey examining the possibility that fuels could cause vapor lock. Results of the survey show that oil companies have contributed to the cause of vapor lock by the addition of alcohol to the fuel without informing the public or advertising the fuel added to "cover up" lower grade crudes and to increase octane ratings . The result of the fuel being adjusted and the octane modifiers was a general increase in the Reid
vapor pressure (RVP) of the fuels (the higher the Reid vapor pressure the greater the possibility of vapor lock) ."

[legomybago]

Im curious to know how many vintage/classic RV'ers have vapor lock issues now, vs. the past? How common is it these days?

[Turbodime]

Ok I think I have it figured out.  The 3-port fuel-sending unit for the RV P30 chassis is NLA as far as I can tell. If I want to use the electric in tank pump for the carb'd 454 I need to use the 5.7L fuel-sending unit.  The 5.7l is a TBI engine, so you don't want this pump just the fuel sending unit.

TBI systems like to run on 12ish psi and the pumps can produce twice that.  So a TBI pump would work because there is a pressure reg just out of the tank but the pump would be out of its optimum pressure curve and there would be undo strain/heat on the pump.

The genset picks up off the return line coming from the mechanical pump just like Kev said. The return/gen line ends halfway down the sending unit. This lets the gen pick up its fuel from the tank and once the tank gets below this line it loses suction and then the gen shuts down. This is a safety design so the gen doesn’t suck your tank dry. 

The 6.2L/6.5L diesel comes as a 2 or 3 port-sending unit. The down side is, the return port ends high in the tank so when the engine is off the gen set wont run as it will lose suction via this port.

So in short, if you want to run the in tank pump use a 454 pump and strainer plus the 5.7l TBI sending unit.

If you want to run an external electric pump outside the tank, good luck as the 5.7L sending unit has the return at the bottom and the supply half way down to connect to the in tank pump.  I could switch the line and suck off the return line but I haven’t figured out how to adapt a strainer.

I could lengthen the return line on the diesel sending unit and this would allow my gen set to pick up the fuel without the engine having to run.

This is what I have found so far and if I find it to be wrong I’ll edit this post.

[DaveVA78Chieftain]

For TBI, the regulator is built into the TBI unit on the engine.  Return line connects to TBI unit.

Will any of these work?

http://store.stepvanparts.com/GM-FUEL-SENDING-UNIT-81980.HTM

http://store.stepvanparts.com/GM-FUEL-SENDING-UNIT-FILTER-81975.HTM

http://store.stepvanparts.com/GM-WORKHORSE-FUEL-SENDING-UNIT-81950.HTM


Mill Supply Inc. (Stepvanparts) is a big supplier of many P30 chassis parts.

Dave

[Turbodime]

Those will all work but none are optimum for either an in tank pump or a external pump. 
The easiest route is the 5.7l sender with 454 in tank pump.  The downside is,  the return line is also the genset pickup line when the chassis engine isn't running.

This return line picks up off the bottom where there could be sediment as well as the potential of the gen running the tank dry. Running the tank dry is a not really an issue for me.
I could just drill a small hole in this return line to keep the tank from being ran dry by the gen.   I also would install a filter at the generator to catch any sediment.

I could weld an extension tube on the 6.2l diesel return port so the gen could use this as a pick up.  I cant tig that great so I'll probably just use fuel injector hose and a quality hose clamp to extend it.

[legomybago]

Sounds like you have it figured out... good job...I dont understand why any manufacturer would install the genny fuel source off the chassi engine fuel return line?? That to me makes zero sence to me...I'm glad I have 3-port sending units on both my rigs!!

[Turbodime]

Tank is back in my possession.  Muffler shop did a good job of getting the varnish off but I was in a hurry so I took it back and finished it up with muriatic acid.  Rinsed with copious amounts of water, then I vacuumed it out and added oil and gas and sloshed it around to keep it from rusting.  When I get it home and if it needs it, I’ll add some phosphoric acid to seal it then re-add oil.
I have this rig in front of my house and I’m feeling the HOA breath down my neck so I took the plunge and picked up a what will work the quickest. It’s a 5.7l TBI fuel-sender and the carb’d 454 pump, screen, gasket, and lock ring.  I’m going to add a filter at the gen if it doesn’t already have one.  I should have the 3gal temporary boat tank off the roof by Sat afternoon.
Next projects are shocks, engine r-12 a/c, unused propane coach heater with squealing bearings etc. etc…..
My buddy asked me what RV stood for. I thought about it for a while, and couldn’t think of anything PG so I said tell me Mr. Stands there with a smirkey smile on your face! He said “Ruined Vacation.”
Blah, I told him to hit the road with those bad vibesJ

Thanks for your help guys.
Aaron

[Turbodime]

Took all day today installing the tank and new lines. I finally found the fuel filter between the propane tank and frame. I had one of my sons hunt it down. I had to jack up the front to get under it to change the filter out.  It was the original filter and once I had it out I banged on it to see if anything would come out, nothing did.


Started it up and headed to the gas station. We hopped out and I took a look underneath to make sure we didn't spring a leak and sure enough, the fuel pressure reg was leaking. I suspected it was the diaphragm and once we got it home and apart it was cracked.  I'll pick up a new one tomorrow.

Things are coming along smooth. I cleaned up the engine and put in a new thermostat and all new vacuum lines.
\

[Stripe]

Nice.

[Turbodime]

Spent 1/2hr on the phone trying to locate a simple Holley diaphragm. Oreillys speed shop had one. No napa, autozone,BAP, or any oreillys had them in the Phoenix area. I got lucky and called the Oreillys that is full of hot rod parts.

Note to self, but an extra diaphragm.

Got the part and gave it to my 11yr old son Gabe and he installed it. Went and filled it up and picked up the family for a nice drive. Drives nice and straight, shifts smooth and stops great.

Glad

[Stripe]

Nice..

Go Gabe...