380 SLC ? fuel or electrical problem.

[RSO 1R]

Hello all, i am recommissioning a 1980 380SLC.It had sat for approx 8 years until earlier this year when the then owner started to work on it.
Work stopped and i made the purchase of RSO 1R intending to bring it back to life. I drained and cleaned fuel tank, fitted new fuel pump and filter.
The fuel distributor had been recently renewed.
My problem is the car starts instantly but dies out within seconds.
I did notice on first start up it runs fine (at fast idle) for approx 20 seconds before dying out as in lack of fuel. If given throttle while running it stops immediately. Further attempts to start are accompanied with a shorter running period until it will not run at all.
I have noticed a small unattached vacuum type hose towards bottom center of driver side cam cover, should it be connected to ??
Can anyone advise if i have a fuel or an electrical problem and where do i start checking.
Any response will be greatly appreciated.
Eugene.

 

[RSO 1R]

Can i add, engine started and ran for 20 mins. until switched of. When running it sits at 1100 to 1200 RPM. Tick over uneven ie, oil pressure gauge fluctuating between 1.2 and 2 bar. No exhaust smoke. I am wondering if i should remove and have injectors checked. Can they be replaced, if ok, using their origional seals/washers/ Is there any other checks i can make at this time ? I have never had fuel injection on any classic before hence the basic question and lack of knowledge. Thanks.

 

[219]

Hi , nice car you have bought .

I had a problem with high idle on my 500SEL when I first got it . The idle speed on these engines is controlled electronically and often a lot of the niggles on these cars is caused by deterioration of the circuit boards in some of the electronic modules .

If you are handy with a soldering iron , you can avoid the great expense of replacing these components .

The ones to check are

1) Over Voltage Protection relay - this one ( on my W126 at least ) is located in the plenium chamber about midway across in front of the windscreen - it is a tall , narrow relay with a fuse on top . If the unit is not in the same place on your car , try behind the battery or in the passenger footwell .

2) Fuel Pump Relay - this one is about the size of a packet of cigarettes and on my car is located next to the brake fluid reservoir - it usually has the work 'Kickdown' or an abbreviation written on the top .

3) Lastly the idle control unit - similar shape and size as the FPR , this one usually has 8 Zyl and some other specs on top .

In all cases , you can ( carefully ) open up the unit by prying the external case away from the base with the pins coming out ( with OVP , remove the fuse first to make disassembly easier ) . The case will usually slip off , revealing the circuit board .

If you flex certain components , you may well see that the solder holding them to the board has crystallised ( dry joints ) or may even have broken away altogether leaving a circular gap around the leg of the component and no longer contacting the track .

This is where soldering skills come in handy - simply re-solder the joint to effect a repair . I took all the modules out of my car and went over all the boards - result 100% reliability , instant starting , smooth and steady idling .

The picture below shows the Fuel Pump Relay ( with Kickd on the top ) nearer the camera and the idle control module behind .

Another shot showing them from the opposite side

Although your 380 is of a slightly earlier generation than the 500 or 420 , it is still basically of the same series of engines so should be very similar in operation . The underbonnet layout on the W107 , though , may differ somewhat from the W126 .

Re the vacuum pipe you asked about - I just looked at my car - there is a thin vacuum pipe coming from somewhere under the air filter housing and following the brake servo larger diameter vacuum pipe - this thin pipe connects into a rubber vacuum manifold along with another three pipes just next to where the servo vacuum pipe goes through the bulkhead .

Hope the above is of help

Good luck .

Which part of the country are you in BTW ?

 

[RSO 1R]

Hi Derek, many thanks for your valued response. I did check the FPR for dodgy joints, all ok. Will try and find the idle control unit as idle is much to fast. I am concerned with the erratic idle and poor throttle response. Given the car had sat for so long i believe the injectors need attention. Never tackled injectors before so any words of wisdom will be appreciated. Car is prepared/booked for MOT and hope to have fuel issue sorted . I am located in N.Ire. Eugene.

 

[RSO 1R]

Have got back to the 380 SLC. Some progress. Running very well when up to 90c on temp gauge.When cold and during warm up one would believe it is off 2 cylinders. the only way it will start from cold is with no throttle being applied. Then i have to allow it its own time to warm up as any throttle applied will cause it to stop. Even when when temp is up to 80c it still has a miss as if off a plug ( new plugs and dizzy cap fitted) but when at 90c appears to run without a miss and no issues when given sharp or steady throttle increase. Have put FORTE injection cleaner into tank.
Will appreciate any advice as to how to cure these symptoms.
TIA
Eugene.

 

[dinoy]

i have experience sluggish drive unless temp is over 40c and that was because faulty air meter small cylinder thing between 2 banks of the v8, 2 solutions to that problem dirve it like bicycle until 1/4 of mile and it opens, wait for it warm the engine up, replace said unit.

it could multi fault, yr engine is the same as w126 1981 - 1985 so parts should be avail from other doner cars and not too expensive

 

[RSO 1R]

Many thanks dinoy. i will check it out.
RSO1R