Hey Folks,

Waking up a '73 280SE 4.5 after a 13 year slumber. First step was making sure there was spark - cleaned the points and installed a new battery. Starts and runs briefly on starter fluid, so compression/spark are at least present.

Fuel on the other hand...

First stop was fuel pump (doa) and filter (very old and full of some very sticky shellac). The fuel tank was (thankfully) empty with just a little buildup in the bottom. Flushed with a couple of gallons of gas and it ran clear and strong. Small victory. Could not get compressed air through the fuel line, so I bypassed it.

Cleaned the pump and bench tested it. Didn't do much so on a whim I tried CarQuest - they have a fuel pump that lists as a replacement for the 280SE. For $50 it was worth a try. Seems to work OK, but I have yet to verify the pressure is in the 30 psig range.

Which brings me to the point - the fuel pressure regulator. There are two regulators on the 4.5 - I believe the first is simply a damper of sorts, and the other (one inlet and two outlets) sets the actual pressure. At this point, I have fuel pressure up to the second regulator but not through it. I took it off and cleaned it. You can feel the spring pressure inside by pressing with a small screwdriver. It seems to me that the amount of pressure it would take to pass fuel through it would be extreme. I bypassed the first regulator and tried to get fuel through it straight from the pump, but still no luck. The fuel backpressure when I removed the line was quite strong.

So, the question is have I got too weak a fuel pump or is it when the regulator fails it does so in the closed position? I might try putting 30 psi of air through it tomorrow and see what happens.

Once I get fuel through it, we'll see if I can get some through the injectors...

Thoughts?

__________________
1973 280 SE Project
1974 280C Project
1975 450 SL (sold, ruined by new owner)
1973 280 SE (sold, never should have)
2006 Dodge 2500 4WD Cummins (best ever)
1983 Land Rover Series 3 88"
1999 Land Rover Discovery 1 (wife's toy)
1968 Piper Cherokee 180D (most fun of all)

First of all, the carquest pump maybe OK for a test, but not long term.

Check this thread out
D-jet fuel pump acting up

Fuel enters the fuel rails at the front and the flows down both sides. The flows come together again at the fuel pressure regulator - It has two inlets and one outlet. this one outlet connects to the fuel damper and from there fuel flows back to the tank. From your post, it sounded like you may have thought the fuel flowed the other way? I have never tried it, but I doubt you could get reverse flow through the regulator.

Maybe try soaking the pump, regulator and damper in carb cleaner or similar. Try blowing through them the proper way. Dismantle and have a look at the pump internals and check that there is resistance across the terminals. Try hooking 12v to pump with head off and see if the spindle rotates. You may be able to bring the pump back to life!

To test the pump, reinstall it and run the discharge line into a container. Pressure should be about 30 psig and low 2L/min.

You will probably need to get the injectors cleaned - there are places that will do it for under $20/injector. But for a start, try soaking them in carb cleaner or an injector cleaner.

Have fun

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Hey Graham

Yes, I had it ass-backwards. Grrr... I was lead astray by the fact the the return line (I know that now thanks to you) was piped to the fuel pump. I asume the pump should be attached to the outlet on the bottom of the tank and the return line goes into the tank up at the top? Just want to make sure the last "experimenter" didn't get it all wrong.

Anyway - I was concerned that the CarQuest pump was not going to cut it long term, so I forked over the $202 for the Airtex pump today. I'll have it in the morning. I've pulled and cleaned the fuel rails, injectors, etc. Cut new FI line sections and picked up some new clamps. I'll assemble it all tomorrow and give it a try.

Someone had attempted to rework the old pump as well at some point and it is ragged. Beyond saving, but thanks for the advice.

To be continued...

__________________
1973 280 SE Project
1974 280C Project
1975 450 SL (sold, ruined by new owner)
1973 280 SE (sold, never should have)
2006 Dodge 2500 4WD Cummins (best ever)
1983 Land Rover Series 3 88"
1999 Land Rover Discovery 1 (wife's toy)
1968 Piper Cherokee 180D (most fun of all)

I have attached a diagram from the MB epc - lower left should be like your car. Item 200 is line from tank to damper and then into pump suction.

Is the Airtex pump a rebuilt exactly same as original? I seem to recall they also had one with an external rubber sleeve that would fit, but likely did not have the internal relief valve.

Unfortunately it is very expensive to get the right pump. I eventually found a new one in stock for about C$500.

(Posting the info below for future reference by me and anyone interested!)

Some other cars use the same pump - I think one of them is an early Nissan ZX but others are Opel, Saab, etc. Bosch pump number is 0580464005 or 61405. There was a pump for sale on eBay and the auction listed that it was applicable to these cars:

Part number 0580464005

APPLICATION GUIDE:

MERCEDES-BENZ 280SE (1971 - 1972)
MERCEDES-BENZ 280SEL 1971
MERCEDES-BENZ 300SEL 1972
MERCEDES-BENZ 350SL 1972
MERCEDES-BENZ 450SE (1973 - 1975)
MERCEDES-BENZ 450SEL (1973 - 1975)
MERCEDES-BENZ 450SL (1973 - 1975)
MERCEDES-BENZ 450SLC (1973 - 1975)
NISSAN 200SX (1980 - 1983)
NISSAN 280Z (1975 - 1978)
NISSAN 280Z 2+2 (1975 - 1978)
NISSAN 280ZX (1979 - 1983)
NISSAN 280ZX 2+2 (1979 - 1983)
NISSAN 280ZX 2+2 GL 1981
NISSAN 810 (1977 - 1980)

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

The 4.5 has come to life. Needed a bit more tweaking to get the fuel injection working correctly, but it starts and runs consistently now. I replaced every inch of rubber fuel line. Cleaned the injectors, trigger points, replaced the fuel pump (Airtex) and battery, cleaned the plugs and points and she's alive. Took a week, couple of hours each night after work. Not bad after sitting under a tarp for 13 years.

I let it run for a half hour. Temp stayed in range, oil pressure is good. No alternator light on, so it seems most systems are functioning - at least for now.

After warmup, the engine starts surging - the fuel pump is cutting in and out. Keeps running, but something is breaking down at temp. Any thoughts?

I am going to have to move it out of my driveway - the blue cloud is not going to make me popular with the neighbors...

__________________
1973 280 SE Project
1974 280C Project
1975 450 SL (sold, ruined by new owner)
1973 280 SE (sold, never should have)
2006 Dodge 2500 4WD Cummins (best ever)
1983 Land Rover Series 3 88"
1999 Land Rover Discovery 1 (wife's toy)
1968 Piper Cherokee 180D (most fun of all)