I guess most cars now a days have them, but my car had the kind mounted to the block. Seems like a lot easier to work on. So anyone know why in tank fuel pumps started being used?

 

Block mounted pumps have their own set of problems. Biggest issue with a FI car is they wont maintain a high enough fuel pressure. High RPM use and block mounted pumps dont get along well either for the most part. Heat is also a problem with those, ever heard of vapor lock?
Electric pumps are just a better deal all around. I think most of the reason they are in the tank is to keep them cool, they last longer that way. They are also supposed to be mounted as close to the tank as possible, cant get much better than sticking it right in the tank.

 

With a block mounted pump it has to "pull" the fuel from the tank, this is inefficent and requires a VERY strong pump. To get the kind of pressures needed for FI would require a very strong pump to pull all that fuel and strong = expensive. The intank pumps are of the "pusher" design, which is more efficent and easier to build, they also require less current to run.

 

Thanks for the answers, I figured it was something easy, just didn't know. I'd still rather pay some money for a higher volume fp block mounted kind then have to change out the one in the tank.

 

so uh.. what happens when the wires going to that tank mounted pump short out? (if they do for what ever reason)

 

If you expect a BOOOM ! ! !

you will be dis-appointed. The fuel tank is a fuel rich environment. Sparks occur in the fuel tank all the time, but there is no explosion because there is too high of fuel to air ratio.

There has to be fuel, oxygen, and heat for fire. Take away one leg of the equation, and no boom

 

well thats good to hear

 

That's right... in fact, if you do it right, you can actually put a match out in gasoline. (don't try this at home)

 

you're absolutely right

 

Not that it's neccessary, but the further explanation of y you can do such an absurd thing as put a match out in gasoline is that liquid gasoline is not flammable. Only the vapors are.... hence when you have a good air / fuel mixture you'll get better horsepower...etc. Because you're buring the fuel more completely.

 

:sillylol: :sillylol: :sillylol: :sillylol: :sillylol: :sillylol: :sillylol: :sillylol:

LOL

 

You may have both types of fuel pump in your car...I see that it is an 86.

Many of the thirdgens had an in tank pump that pushed fuel to the mechanical on the block.

 

Almost all car applications after 87 had their fuel pump inside the tank (in 88 everyone went FI). The advantage of having an in tank pump is mainly lower noise levels, lower potential leaking problems, less mounting sensitivity of the pump and lift of fuel from the tank is minimized.

 

I also have an '86, so now I'm curious, what's the easiest way to tell if you have both an in-tank and a mechanical pump? Also, if I have an in-tank pump and want to change my car over to fuel injection, would I just have to change the intank pump. Is the wiring and sending unit good to go?

 

Cole,

I have an intank carb pump and am switching to FI too, i talked to a mechanic at a chevy dealer and he said that i just need the FI pump and the sender is the same. he also said the connector for the pump may be different but wasn't sure.

as far as telling if you have an intank pump, turn the key to on but dont start the car, you should hear the pump run for a couple seconds to prime the system or see if you have a fuel pump fuse

 

Kinda a similar question, why couldn't they have just used a good seal and mounted the pump on the bottom or side of the tank instead of an impossible to reach spot at the top?

Will

P.S. I say this being a bit bitter after having just replaced my fuel pump and breaking a brake line in the process.

 

glad to see you found the search icon, lot of people miss it. reason you don't see a pump mounted o nthe bottom is the "good seal". you'd never get it plus the lines would be much more exposed.

 

Did the crossfire injection cars come with a tank mounted pump, or the mechanical block design?

 

I don't know what you are talking about RE: everything being FI in 88. Lots of foreign manufacturers had carbed vehicles at that point.

GM still did as well, the Olds 307 was carbed until production ceased in 1990, and went into lots of fullsize RWD vehicles. All with block mounted fuel pumps.

 

For our purposes here, everything went to fuel injection in 1988... Who cares about other manufacturers? Especially foreign ones?

 

Chevy Caprice used a carbed Olds 307 up to 1990.

 

It was an EPA deal; supposedly manufacturers as of 1988 were supposed to start using fuel injection. I dunno madmax told me I blame it all on him

Where was this thread dug up from anyway?

 

Seeing the comment about an 86 car having both electric in tank pump and a mechanical one, I'm curious.... My 85 iroc has both, however I had put it down to the fact that the 350 engine is out of a 79. I had thought that they had eroneously left the fuel pump on the block as they had no blanking plate.

Should I leave it as having both pumps, as that is how it was designed to work, or wot?

Cheers,

Si. :lala:

 

According to what I recall of my factory manual, they were block mounted.