Low Power, Dies After Revving
 

1983 300CD

Car is finally running, idling nicely, and warms up just fine...however, it has almost no power (in any gear) when I attempt to take it out on the road. It just creeps along, takes forever to rev up, and will not climb even a small hill. Once it does rev up, it will typically immediately die when I let off the throttle after the rev up. Also, after it is warmed up, if I rev it up in neutral, it will immediately die when I let off the throttle after the rev up. It starts right back up after it dies. If I rev it up when cold, it does not die.

I've checked all the normal stuff:

1. Throttle linkages are fine
2. No dragging brakes
3. All fuel filters (including the tank strainer) are good.
4. Good fuel in the tank
5. It has what I think are good compression numbers (1-360psi, 2-395psi, 3-405psi, 4-390psi, 5-360psi)

I'm starting to question if maybe there is a transmission issue. Any other thoughts?

Have you adjusted the valves?
Have you changed the Air Filter?
Does it *smoke*?
Did you *pop* test the injectors?
How many miles do you think it has on it... leading to the next line...
You should Check the Timing Chain for stretch...
What temperature is it running @? (when warmed up and driving)

Transmission
Have you changed the transmission fluid and filter? (use Dex/Merc) DO NOT FLUSH
Have you changed the rear end oil?

It sounds like you are losing fuel when you are letting off the pedal... could it be ALDA related ...

Did you replace *all* fuel filters (you said they are *good*... but, did you replace them with new)?

Those compression numbers are EXCELLENT! Was the engine stone cold when the compression test was done?

Yes I adjusted the valves.
Has a new air filter.
Smokes very little. Very little blow by.
Greazzer did the injectors so I think they are good.
Has about 220k miles.
I have not checked the timing chain at all.
It runs a little over 80C.
I have not touched the trans or rear end.
I replaced both fuel filters under the hood and I checked the strainer when I drained all the fuel to make sure it was fresh.

I thought the same thing about losing fuel when letting off the throttle but I don't know how to test this.

When I say it has low power, I mean it will barely creep along with the pedal completely down. The tach is not currently working but the RPMs seem to match the speed. In other words, it's not revving at like 8k but only going 5mph.

Engine was stone cold when I tested the compression. I tested through the injector ports using the snap on adapter that screws right into the port.

I pop test and calibrate my injectors when I do the the compression test... its just very easy to do them both @ the same time.

Well... it seems that you have the basics covered. So, you need to check the timing chain for stretch... after that you can go after the IP (Injection Pump). Darn... what is the name of the Rack Adjustment Bolt on the IP??? Someone will chime in here.

Ask if the injectors were pop tested and at what bar/psi they popped at?

I'm going with fuel delivery here... just don't know what yet... let me think a few...

Try driving it wit the oil fill cap removed to assure that internal engine pressure is not pushing the shut off valve partly closed.

Checking Timing Chain Stretch.... There are two key locations with alignment marks.

The first is located on your engine counterbalance and is marked of in degrees of rotation (usually in 5 degree increment marks. There is a pointer coming off the engine block that points to the position of the crank in relation to top dead center (tdc) on number one cylinder. When the pointer is at zero degrees and both valves are closed (you can feel play in the rocker arm) on number 1 cylinder your engine is a TDC (with piston coming up on compression stroke). ( The marks will not tell you if you are 180 degrees off - you have to refer to the closed valves to confirm TDC. If one of the valves is opened then it means you are off by 180 degress of rotation.

The second location is at the front of the camshaft right behind the sprocket. You will have to remove the valve cover to see these marks. There a a v notch cut in the spacer that sits on the end of the camshaft just behind the sprocket. On the forward cam tower there is a raised arrow as you see in the picture below. The arrow should line up with the notch when the engine is on TDC and both No. 1 cylinder valves are fully closed

YES... I just grabbed this quick from Ken's site... Thank you Ken.

Good One!

I tried it for a while with the air cleaner assembly off, which left the PCV (?) port on top of the valve cover wide open. I think this would accomplish the same thing as leaving the oil fill cap off.

Could a bad/stuck EGR valve cause this sort of issue?

I think not... however, I Delete the EGR *very* shortly after purchase.

You had the valve cover off ,you might have simply miss located the bowden cable location .The bowden cable joint and the cruise control conrod joint are within an inch apart and are commonly misplaced especially if the cruise control has been deactivated (all its conrods removed)The slack, or lack of plays a big part in the engine and trannie recognizing each other.I had the same happen after doing a valve adjustment ,recheck the bowden cable .

This is a good thought, but I'm pretty sure the Bowden Cable is hooked up correctly based on an earlier thread I had where another member (Funola) very kindly provided images of his linkage setup for comparison. Mine was identical, although embarrassingly more filthy.

Another possibility is really poor fuel pressure to the base of the injection pump. Say a weak lift pump. Or the relief valve might be staying open.


Those are the two things I might checkout first. There are a couple of more things but not common.


A quick test is does the primer pump become more resistant as you pump it? If so the relief valve is working. Next have someone pump the primer pump with the engine running and see if the engine no longer quits when at hot idle. These two tests are not hard to do.

Also good thoughts, but I had Greazzer rebuild the lift pump with a Bosch kit and bought one of his rebuilt relief valves. I had an issue a few weeks back where the car wouldn't start at all after tons of troubleshooting I'm pretty sure it was just air stuck in the lines, but in the process I replaced or rebuilt about all the wear parts in the system, including the primer pump.

The primer pump does become more resistant when I pump it, and I can hear the relief valve working after several pumps.