Fuel System Flush

[Bill6298]

Does anyone know the proper inner diameter size for hoses that go from the fuel pump to the supply & return hard lines? I'm trying to temporarily connect these hoses to a cheap pump to flush my hard lines.

Hard Lines - Front.jpg
Cut Hoses.jpg

I have the older red/orange hoses and I initially thought they were 5/16". I tried to connect a hose to the metal 5/16" fitting on the cheap pump. No luck. Then I tried to connect them to these cheap universal filters with 1/4" plastic fittings. No luck as well.

41AWAR2EBRL.jpg

I can't get anything to fit. It seems like the inner plastic of the hose is too tough/stiff to fit properly. I can barely cut them with a razor blade.

At this point I think I just need to cut the hoses off the hard lines. I'd like to get some cheap low pressure hoses for this temporary flush. I will eventually have proper DMC replacement hoses but I'm trying to clean things up before my parts arrive.

I tried to search for diameter size and also check the manuals. No luck there either.

[Bitsyncmaster]

Most of us with those orange lines have cut them off and replaced them with rubber fuel hose. If you cut them off you should not have any trouble using any soft fuel line to flush.

[Bill6298]

Most of us with those orange lines have cut them off and replaced them with rubber fuel hose. If you cut them off you should not have any trouble using any soft fuel line to flush.

Any idea on the size for the hard lines? I'm still searching and reading threads but can't find anything.

Thanks

PS - I actually did find one thread where you thought they were 5/16" from memory but the OP did not respond back. To me, it seems like the ID of my current hoses are 1/4" but they are so internally mangled it's hard to measure.

[DMC5180]

1/4 inch (6 MM) Fuel injector hose is what you need. Every auto parts store has it in bulk. Cut the old Orange lines off the fittings and replace them with the new Rubber FUEL INJECTION High Pressure Hose. Not FUEL LINE ( which is meant for low pressure applications). The only way to reinstall the orange hose is to heat it. I've heard of people putting the ends in a small pot of boiling water to soften the teflon inner member then quickly push it on the hard line barb fittings. However, it's generally recommended nowadays to use the soft rubber barrier hose.

[Bill6298]

The only way to reinstall the orange hose is to heat it.

Thanks for confirming 1/4".

I feel a little better knowing that the orange hose is "different". It was incredibly frustrating not being able to connect them to my cheap filters. It never occurred to me that you'd have to heat it up first. I will get a better knife and scrap them. My regular wal-mart utility knife isn't doing the job.

Thanks again!

[DMC5180]

Make sure you install small hose clamps with the softer FUEL INJECTION hose.

[Bill6298]

Make sure you install small hose clamps with the softer FUEL INJECTION hose.

Dennis,

Will do. I have a low pressure pump and some (temporary) regular low pressure fuel line hoses for the flush. I'll make sure I'm using the high pressure injection hoses with clamps when I get the regular fuel pump installed.

Thanks

Bill

[Bill6298]

Thanks everyone for the tips. I finished my flush today.

1 - A heat gun was the answer to get those orange fuel hoses off the hard lines. With heat I was able to use a very rigid knife to peel away the outer layer and then the insulation. This left the inner hard plastic on the barb. A small electronics-type flat screwdriver and more heat split the hard plastic off the barb. Without the heat my best knives could not do anything meaningful without a lot of force.

2 - My Mr. Gasket 42S pump is rated at 2-3.5 PSI and 42 GPH. I was surprised at first how slow it was to run my cleaner and then gas through the system. I was worried the liquid was escaping somewhere where I could not see it or smell it. Even my regular bolt with fender washers and gaskets did not leak around the supply and return lines in the engine compartment. The only leak I found was my cheap $10 filter from Auto Zone.

Bottom line, the flush itself was worth it. The crap that came out at first was nasty. I used acetone and then ethanol-free gasoline. All is clean now.

Next up is getting a fuel pump hooked up, change the accumulator, change the filter, and then put the injectors in jars.

I need to inspect the fuel distributor hoses. I have some small chunks of plastic missing out of my current hoses but none are too deep. I have no idea of the age either. I need to ping my PO. I hate to spend another $200+ for the new steel lines.

[David T]

Thanks everyone for the tips. I finished my flush today.

1 - A heat gun was the answer to get those orange fuel hoses off the hard lines. With heat I was able to use a very rigid knife to peel away the outer layer and then the insulation. This left the inner hard plastic on the barb. A small electronics-type flat screwdriver and more heat split the hard plastic off the barb. Without the heat my best knives could not do anything meaningful without a lot of force.

2 - My Mr. Gasket 42S pump is rated at 2-3.5 PSI and 42 GPH. I was surprised at first how slow it was to run my cleaner and then gas through the system. I was worried the liquid was escaping somewhere where I could not see it or smell it. Even my regular bolt with fender washers and gaskets did not leak around the supply and return lines in the engine compartment. The only leak I found was my cheap $10 filter from Auto Zone.

Bottom line, the flush itself was worth it. The crap that came out at first was nasty. I used acetone and then ethanol-free gasoline. All is clean now.

Next up is getting a fuel pump hooked up, change the accumulator, change the filter, and then put the injectors in jars.

I need to inspect the fuel distributor hoses. I have some small chunks of plastic missing out of my current hoses but none are too deep. I have no idea of the age either. I need to ping my PO. I hate to spend another $200+ for the new steel lines.

You can just wrap the lines with some electrical tape to cover the missing chunks as long as the white braid is not damaged. On the hoses to the injectors, if the inner liner is damaged the hose must be replaced. Make sure the plunger in the mixture unit is able to move freely. Do not reuse the copper washer/gaskets. If the fuel system is all gunked up the injectors should be cleaned and tested.