81 SC Fuel Volume Test

VincentVega · 10-18-2004, 06:17 PM

Hello All- Trying to track down a no start issue with my 81 SC. Going through the fuel tests I am unsure how to properly test fuel flow. The Bentley shows (from a picture) there should be ~1l of fuel flowing with the pump on from the bottom of the fuel accumulator (position A). I get maybe half that volume. But, when I test at position B I easily see 1l. The line to the bottom of the accumulator T's off from the line at position B.

Fuel coming into the accumulator from tank is fine. Same for going to and leaving filter.

Anyone know the proper place to test fuel volume?

Thanks

VincentVega · 10-19-2004, 05:58 AM

am bump

Any CIS guys know how to properly run a fuel volume test?

Thanks

dean · 10-19-2004, 07:14 AM

I don't know if it is correct but if it were me, I would hook up a hose from the output of the filter and measure the volume.

VincentVega · 10-19-2004, 07:33 AM

Thanks for the reply. I tested fuel to the accumulator, from the accumulator and after the filter all ok. If I test at position B in the pic I get good flow, but at A I dont. The manual photo suggest A is the place to check, but I want to be sure.

I'm trying to eliminate a fuel distributor issue if possible.

Thanks again

William Miller · 07:47 AM

Chris, I'll post this on the NOva thread as well.
Now that I see your picture, I recall that the newer / USA SC have a different fuel accumulator. It's smaller than mine and according to this picture has a 3rd fuel connection on the bottom.

The Pet program and Pelican Parts pictures with the parts both show the older system like I have in my 83 ROW SC.

It appears from this fuel flow diagram that the bottom connection is a return to the tank. I don't think you should have any flow there. I have not cut one apart, but I understand that the accumulator (At least my type) has a rubber diaphram in it with a spring below it. The top half should be filled with fuel and the spring maintyains pressure after the fuel pump is shut off. This is intended to help start the car back up after it's been sitting for a while. The test for the accumulator is to check system pressure with the fuel pump on and then then shut it off. The accumulator should maintain pressure (1.3bar for 10 min and 1.1 bar for 20 min)for a period of time. These come from the little spec book 82-83 which I think is the same for your car.

Edit: removed second idea:
One posibility is that it is there just in case the bladder in the accumulator tears. In this case it would return the fuel to the tank.

If you are getting flow out of the bottom that may not be good.
For flow check the line that goes from the filter to the engine. Probably the top connection on the filter? If the floe there is 1litre than you have good flow thru both the filter and the accumulator. If not, it's one of the 2.

Also do the time test on the accumulator. It would probably not normally be the source of your problem but if the diaphram tore a piece of it could clog the outlet to the filter.

William Miller · 10-19-2004, 07:59 AM

Chris at position B, is the reduced flow from the nipple on the accumulator or from the hose? If it's from the hose it's probably normal. Based on the diagram, that hose is part of the side that returns to the tank. First the pressure regulator and other restrictions would slow the flow down, but also some or most fuel would return to the tank as normal.

If you have full flow from the filter to the engine check it at the connection going into the fuel distributer. Then at the system pressure regulator. Maybe see what's comming out of the line going to the warm up regulator. If it's all good at these points the next step is to check the flow to the injectors themselves with beer bottles.

One of the DORKI crew could probably look at it and tell you if the flow looks normal or restricted. You can certainly tell if there is a spray pattern problem or a significant problem with 1 or more injectors.

Hope this helps! Usually the right picture does!

William Miller · 10-19-2004, 08:02 AM

Another dumb question: The connector you show as A in your picture looks like one I have.
Are you absolutly sure you got things hooked up right?
I just had to ask.

Early_S_Man · 10-19-2004, 08:57 AM

Well, the traditional volume test is to pull the output hose from the fuel pump and attach a short hose into a container larger than two liters ...

Run the fuel pump for exactly 30 seconds and measure the output volume. The factory spec book lists 750 ml/30 sec as the minimum volume acceptable.

Also, 8.0 Amps is the maximum allowable current draw for a CIS fuel pump.

VincentVega · 10-19-2004, 09:01 AM

Thanks guys.

Bill - The car ran as you see it to VIR and back just fine, ~1k miles.

The hose that goes to the accumulator is a smaller diameter. The reduced flow was measured by disconnecting the hose to the bottom of the accumulator and sticking it in a coke bottle.

Sounds like fuel is ok. Argh.

William Miller · 10-19-2004, 09:45 AM

Had to ask the obvious. foot in mouth....
I agree that is probably normal. Dis any fuel squirt out of the bottom of the accumulator when you did this? If not that's good too!
What's next?

William Miller · 10-19-2004, 10:06 AM

Chris I found a picture that shows that mine even has the lower connection to the accumulator.
I think the only difference is that for some reason the later ones for K-lambda cars are smaller.
Here's it with and without the engine!

foot in mouth again

VincentVega · 10-19-2004, 10:12 AM

That's a cool shot of your car. No roof/top, no windshield, not deck lid.

William Miller · 10-19-2004, 10:26 AM

Thanks, some of that stuff is back on now. Won't be long and I'll be back on the road with you guy's. You too when we sort out this issue!

labdag · labdag's Garage

Hi would anyone know the nam or part # of the fuel line at bottom of fuel accumulator in Vincent diagram line "A"? The fuel hose on my 83 sc is. Leaking
Thank you