Advice needed 1980 380E

[carat 3.6]

Not sure about twin pumps ? You mean the supply pump from the tank?
The wiring diagram only shows one but these seem to differ country to country.

Yes the supply from the tank. Kjet needs high fuel pressure so it is common on Mercedes to have twin pumps, they are normally in series so if one pump isnt working you will only have half the fuel pressure.

In this form the engine will try to start, but as soon as it fires and demands more fuel the pressure drops off and it stalls.

 

[Kerabo]

Any use?

Thank you

 

[Kerabo]

I keep downloading it but can’t find the download afterwards on my ipad

 

[Kerabo]

I have been viewing these on YouTube. It’s all very precise and compares with the insides of a Diesel injection pump.
I removed the injectors and blow them through and all are clear. A little better than before I blow them through.
Before I connect the injector pipes I am going to fit 6 plastic pipes to the end and see if and when it pumps as it flows through the pipes.

What I don’t understand yet is what powers the pump to injection pump. Does something rotate or pulse?

My thoughts are that when it fires it’s firing on the cold start boost fuel and not injecting but we will see.

Thanks Ken

 

[colinallcars]

I keep downloading it but can’t find the download afterwards on my ipad

It will most likely be in downloads, do a search on your iPad

 

[carat 3.6]

What I don’t understand yet is what powers the pump to injection pump. Does something rotate or pulse?

If you mean the fuel metering head it works on fuel pressure only, there is no electronic power as such. The injectors themselves only open when enough fuel pressure is present behind them, you would need quite alot of air pressure to blow them open. If they need cleaning an ultrasonic cleaner is the best way.

 

[Kerabo]

If you mean the fuel metering head it works on fuel pressure only, there is no electronic power as such. The injectors themselves only open when enough fuel pressure is present behind them, you would need quite alot of air pressure to blow them open. If they need cleaning an ultrasonic cleaner is the best way.

I cleaned the carbon away and blew them through with an airline but it was obvious they needed some pressure so it made me wonder where that pressure came from.

Thank you

 

[Bellow]

I have been viewing these on YouTube. It’s all very precise and compares with the insides of a Diesel injection pump.

Don't go confusing diesel plungers (which are pump pistons) with K Jetronic plungers which are metering only.

 

[Kerabo]

Don't go confusing diesel plungers (which are pump pistons) with K Jetronic plungers which are metering only.

Oh yes I understand that. It was just the amount of cleanliness he was using.

 

[TourmalineE230]

Hello Kerabo, I assume the car your friend has is a W123 280E ?

I think most (if not all) of the Mercedes K-Jetronic (CIS) equipped models don't have in-tank fuel pumps, they all run a Bosch in-line pump with a fuel accumulator and fuel filter (mounted in a carrier under the car close to the fuel tank). The only K-Jet cars I remember having an in-tank helper pump were Volvos (there are probably other OE's too).

From my own experience, K-Jet cars don't like sitting unused for long periods, as the fuel system can get gummed up with fuel varnish (especially the injectors, and the fuel distributor / metering head). Other K-Jet system components that can give issues if left sitting idle for long periods are the warm up regulator and auxiliary air valve. Vacuum leaks can also cause all sorts of problems. Having said all of that, K-Jet / CIS is generally super reliable when maintained as it's comparitavely simple mechanical system.

From your photos I'd suggest your friend consider a new set of injectors (they're still available from Bosch and relatively cheap). Check the control plunger isn't stuck on the fuel metering head (you would have to remove / demount it to check), check the fuel pump is supplying the correct pressure and the accumulator is OK (internal diaphragm fails and won't hold system pressure, more of a hot start issue though).
I think you already mentioned that you were going to check the fuel pump relay.

I have attached a couple of things that might assist a little re. your troubleshooting.

Good luck with it.

 

[Kerabo]

Hello Kerabo, I assume the car your friend has is a W123 280E ?

I think most (if not all) of the Mercedes K-Jetronic (CIS) equipped models don't have in-tank fuel pumps, they all run a Bosch in-line pump with a fuel accumulator and fuel filter (mounted in a carrier under the car close to the fuel tank). The only K-Jet cars I remember having an in-tank helper pump were Volvos (there are probably other OE's too).

From my own experience, K-Jet cars don't like sitting unused for long periods, as the fuel system can get gummed up with fuel varnish (especially the injectors, and the fuel distributor / metering head). Other K-Jet system components that can give issues if left sitting idle for long periods are the warm up regulator and auxiliary air valve. Vacuum leaks can also cause all sorts of problems. Having said all of that, K-Jet / CIS is generally super reliable when maintained as it's comparitavely simple mechanical system.

From your photos I'd suggest your friend consider a new set of injectors (they're still available from Bosch and relatively cheap). Check the control plunger isn't stuck on the fuel metering head (you would have to remove / demount it to check), check the fuel pump is supplying the correct pressure and the accumulator is OK (internal diaphragm fails and won't hold system pressure, more of a hot start issue though).
I think you already mentioned that you were going to check the fuel pump relay.

I have attached a couple of things that might assist a little re. your troubleshooting.

Good luck with it.

Thanks for that.
He fitted the fuel pump himself so I never got to see this. I do see quiet high pressure fuel at the union on the injection pump inlet and this fuel seems to have stored pressure so I think the accumulator I think it’s called is storing pressurised fuel as I think it should.
I have the injectors out and have cleaned them externally and blew them through with an airline and all were able to pass air and spray. They did need some pressure to do this and that’s why I asked where the pump gets it’s pressure from.
After seeing a clip on the control plunger I am feeling this may be the problem.
I have bought some clear plastic tubing and plan to fit this over the injector pipes and just see if any fuel comes out.
As it fires and tuns only a few seconds every time I wondered if it’s running on what the cold start device lets pass.
What’s your thoughts on that?
Thanks Ken

 

[TourmalineE230]

From what I remember Ken, the cold start valve only operates for a very short period when the engine is cold then shuts off (I think it's only a few seconds) , so you may be right that it's been trying to run on that.

I think it would be wise to get the fuel metering head looked at / checked over regardless. Or if you're game to DIY I think the rebuild kits are around 55->60 pounds.

Given the number of times that I've seen a grotty old fuel filter on K-Jet cars (as they're normally underneath the car and/or hard to access), I'd also recommend that you change that too as a precaution (unless your friend can confirm it's been done recently).

Cheers - Ross

 

[Kerabo]

From what I remember Ken, the cold start valve only operates for a very short period when the engine is cold then shuts off (I think it's only a few seconds) , so you may be right that it's been trying to run on that.

I think it would be wise to get the fuel metering head looked at / checked over regardless. Or if you're game to DIY I think the rebuild kits are around 55->60 pounds.

Given the number of times that I've seen a grotty old fuel filter on K-Jet cars (as they're normally underneath the car and/or hard to access), I'd also recommend that you change that too as a precaution (unless your friend can confirm it's been done recently).

Cheers - Ross

I was a bit scared of him ending up with a massive bill if I get something wrong as it’s only a favour to a mate
Thanks again for your help and advice.,

 

[optimusprime]

Check any leaking vacuum hoses and joints ...check and clean fuses and battery connections.Click on the link find that part on your cars engine remove it and clean it out with carb cleaner 380SL 380SLC 380SEC 380SEL 500SEL 500SEC AIR IDLE SPEED CONTROL VALVE 0001411225 - MAF Service GmbH

 

[Kerabo]

Check any leaking vacuum hoses and joints ...check and clean fuses and battery connections.Click on the link find that part on your cars engine remove it and clean it out with carb cleaner 380SL 380SLC 380SEC 380SEL 500SEL 500SEC AIR IDLE SPEED CONTROL VALVE 0001411225 - MAF Service GmbH

Thank you .
Providing the Pump has fuel is it completely mechanical ?

Electrical just for supply and cold starting ?

So if I have a good what seems quiet high pressure supply to the pump and and no injection I can assume it’s the pump and nothing electrical
Thanks

 

[Kerabo]

Well cleaning the injectors through made no difference.
Runs with a squirt of gas so electrical ok.
I will have to remove the top and look inside.

Is the part circled a bleed screw? It looks like one?

Also assuming these for screws hold the top on but why 2 slotted and 2 Torx ?

Have a video of it cranking but dint seem able to load it.

Thank you.

 

[Bellow]

Is the part circled a bleed screw? It looks like one?

Maybe, a last chance filter?

Also assuming these for screws hold the top on but why 2 slotted and 2 Torx ?

Because someone's been inside it before?

 

[Kerabo]

From what I remember Ken, the cold start valve only operates for a very short period when the engine is cold then shuts off (I think it's only a few seconds) , so you may be right that it's been trying to run on that.

I think it would be wise to get the fuel metering head looked at / checked over regardless. Or if you're game to DIY I think the rebuild kits are around 55->60 pounds.

Given the number of times that I've seen a grotty old fuel filter on K-Jet cars (as they're normally underneath the car and/or hard to access), I'd also recommend that you change that too as a precaution (unless your friend can confirm it's been done recently).

Cheers - Ross

I think the unit has to come apart and as skilled as I think I am this looks too technical unless you really know what your doing. Even if I managed to fit new seals and O rings it looks like even a small alteration of any settings is critical.,
I had been trying to work out where the up to 5 Bar pressure comes from but I think if I understand it correctly its from the fuel pump pumping fuel from the tank and then the unit controls it from there onwards.

So does anyone know of any specialists to talk to?

Thanks Ken

 

[carat 3.6]

I think the unit has to come apart and as skilled as I think I am this looks too technical unless you really know what your doing. Even if I managed to fit new seals and O rings it looks like even a small alteration of any settings is critical.,
I had been trying to work out where the up to 5 Bar pressure comes from but I think if I understand it correctly its from the fuel pump pumping fuel from the tank and then the unit controls it from there onwards.

So does anyone know of any specialists to talk to?

Thanks Ken

I think your jumping the gun a bit here, a rebuild on these is often not needed. The 6.5bar of fuel pressure does indeed come from the fuel pumps at the rear, the metering head on the engine just sends it where it needs to be.

You still need to confirm some of the basics:

1. has the fuel filter been changed?

2. if it has two pumps and both are working?

3. on the side of the metering unit is the EHA valve, check the o rings inside are not split.

4. under the metering head is a rubber boot, check it for splits causing a giant vacuum leak.

 

[Kerabo]

I think your jumping the gun a bit here, a rebuild on these is often not needed. The 6.5bar of fuel pressure does indeed come from the fuel pumps at the rear, the metering head on the engine just sends it where it needs to be.

You still need to confirm some of the basics:

1. has the fuel filter been changed?

2. if it has two pumps and both are working?

3. on the side of the metering unit is the EHA valve, check the o rings inside are not split.

4. under the metering head is a rubber boot, check it for splits causing a giant vacuum leak.

I have to admit the filter has not been changed but there is lots of high pressure fuel reaching the unit. The cars owner has changed a fuel pump but there are defiantly 2 ?
I don’t know the EHA valve but will look it up and check it.

Looked up the EHA valve but don’t recall seeing anything electrical on the unit.

Do you mean a boot that joins to I think the manifold ?
Thank you