Pagoda SL Group

W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: FresnoBob on June 20, 2019, 21:19:25

Title: Very little fuel returning to tank
Post by: FresnoBob on June 20, 2019, 21:19:25

I've read that you should measure 1 liter per 15 seconds after the fuel damper.  Mine was barely dribbling out of the hose, so we removed the fuel pump and cleaned the screen, which was clogged with small particles of rust and dirt.  However, the fuel is still flowing back from the damper at a very low rate.  There is now at least 1 liter / 15 sec of flow into the filter, which is rather new.  Is there any other filter or screen in the system? 

Title: Re: Very little fuel returning to tank
Post by: Benz Dr. on June 20, 2019, 22:40:21

There's a screen inside the fuel tank but I don't think that would be your problem.

I've seen where the fuel pressure regulator can cause return flow problems but without knowing which IP you have it's hard to say. If you have good flow out of your fuel filter keep moving down stream until you locate the problem or you find an area where fuel flow is reduced. Figure out what's causing that problem and you have your answer. 

Could also be a hardened diaphragm in the fuel damper.

Title: Re: Very little fuel returning to tank
Post by: FresnoBob on June 21, 2019, 00:09:47

Thanks Benz Dr.

I have a 1966 230 SL, and I thought there was only one IP used on those cars.

I ordered a new fuel filter and spare today.

I’ll check flow out of the filter, but for convenience, can I check this at the CSV?

Title: Re: Very little fuel returning to tank
Post by: Benz Dr. on June 21, 2019, 02:08:39

You can check it at the CSV. 230SL's all used the same injection pump that was only used on that engine.  I've seen where the plate inside the fuel pressure regulator became jammed and fuel pressure couldn't be maintained or reached to obtain enough pressure inside the IP. You need at least 10 PSI or the engine won't run well and 15 PSI is perfect.

Title: Re: Very little fuel returning to tank
Post by: Bonnyboy on June 21, 2019, 16:38:37

I would also check the fuel line running back to the tank - mine was crimped just at the bulkhead and was covered by the undercoating so I couldn't tell. I just worked backwards from the tank until I got full pressure and went from there. 

Title: Re: Very little fuel returning to tank
Post by: FresnoBob on June 25, 2019, 23:37:57

I replaced the filter, cleaned the screen in the fuel pump and also blew out the inlet nozzle to the injection pump.  Now I have roughly 1 liter per 15 seconds of flow back to the tank.  Thanks everyone for the suggestions. 

Car still doesn't idle until it is fully hot.  Completely frustrated with my WRD, shims and trying to get the cold to warm idle higher. 

Title: Re: Very little fuel returning to tank
Post by: mrfatboy on June 26, 2019, 01:39:46

It's good to hear you got some things sorted out👍

Bring us up to date on where you are at currently with you cold idle problems. Are you rich or lean?