unit505

My buddy is working on a 74 ford C8000 with a 392 gasoline engine. It is a fire truck. He says it has a single fuel tank with 2 electric pumps on the tank and a mechanical on the engine. He can only guess that due to the length of the truck, the factory installed the electrics to serve as a jockey pump for the mechanical. Anyone ever heard of a mechanical and electric pump operating at the same time?

GhostriderI

Is he looking at the fuel or botton of the water/foam tank? Got Pic?

unit505

No pics, but he has dropped the tank four years ago and knows for sure that it's the fuel tank. He said the electrics used to cycle when the key was turned and now they don't. He's trying to figure out if he has a relay or pump issue, but is unclear as the purpose of three pumps. Two electrics, one feeding the other and out to the mechanical. One of the electrics has a return line to the tank. The mechanical feeds a holley double pumper carb.

GhostriderI

If there is access to the wiring to the pumps check for power at the pumps when someone turn the key to the on position if you get power I would then look at the pomp If not the wiring or relay, my best guess not working on it. Question is the battery week? if so that could also be part of the problem.

unit505

He's in the process of locating the electric pump problem, but I was trying to figure out if the electrics were actually stock or aftermarket and if he really needed them. I've seen some emergency vehicle conversion companies do some crazy stuff though, and the fire truck company is no longer in business. Without original build documentation, these emergency vehicles are sometimes a complete mystery. We've had to completely stip the wiring from ambulances only a few years old and completely rewire them to have any understanding for future maintenance. I did some research and have found a few hot rod guys running both electric and mechanical pumps, but can find no info on a factory setup. My buddy says that the wiring for the electrics are fully encased in the factory wiring harness coming to the rear of the vehicle and appears to still have the factory tape around the wire loom. Strange setup. I've worked on allot of firetrucks over the years, even a 67 Ford Milk Truck converted into a water tanker that is still in service today. These trucks were so simple to work on, but I've never run across one with both mechanical and electric pumps. I thought that maybe, at some point, the truck had an second engine for pump and roll capability and needed a fuel source, hence the electric pumps, but he says the department has had the truck since brand new and it never had a secondary pump engine. I have installed a 10hp briggs water pump on an old fire truck and used an electric pump to feed fuel to the briggs and straton from a drain **** on the trucks fuel tank. It worked great and made for a fantastic pump and roll brush truck. This thing has never had an option like that though and the setup is crazy. It has what appears to be an original mechanical pump, so either the factory used dual electric pumps to help jockey fuel from the rear of the truck where the tank is or the original pump was worn out and they elected to go with electrics to feed it. I don't know why they would do that when the stock fuel pump is still readily available, except the fact that this little town is just now discovering the internet. Lol. I'm going to suggest that he replace the stock mechanical pump and to take a few minutes and take the electrics out of line and test it to see how the truck runs, if at all. Seems it would have been easier to block off the stock mechanical and run straight to the carb with a single electric pump.

GhostriderI

Depends on the pump, Ford in the past has used one pump to help another, like in the '80s with the f-150 and broncos the used a low pressure pump in the tank and high pressure to get to the engine but electric. I wonder if this could be a simalar setup, but with electric priming mechanical. Let me look around and see what I can find to help ya'll

GhostriderI

Also everything I have seen on the C8000 is that it is a Diesel so this may have been a special order

Also this may interest you http://www.ebay.com/itm/FORD-1974-Br...497825&vxp=mtr or maybe this one http://www.ebay.com/itm/COMPLETE-197...105552&vxp=mtr hope these may help

unit505

That's an awesome find. Thanks. I actually saw a video of the truck when it was running and I swore it was a diesel. He assures me that it's gasoline and he was sober.......Lol, and the Assistant Fire Chief, so I can only assume he's right. The two electric pumps that he's describing could be low and high pressure pumps feeding the mechanical. If he's swapped a high pressure for a low pressure, that might be an issue too. Thanks for the help. I'll be back in the office on Friday and talk more with him about it.

zzpatrick1

Kinda seems opposite of what it should be. Doesnt it? Wierd set up...

GhostriderI

Bump Any updates?