Hi so I recently got a 85 300TDT and have been fixing it up and so far it was running well and starting just fine. A couple weeks ago it was hard to start after i had driven it for a whiile then parked, once i got home i was unable to get it to start at all, just cranks and cranks. The next morning you can walk right out and start it no issue, even when parked with the nose up. I have done a bunch of different things to the car and it behaves exactly the same way. So far to fix this i have cleaned the tank strainer, passed some weedwhacker string through the fuel lines, changed both filters, valve adjustment (which made amazing difference), changed all hoses, cleaned all surfaces and replaced crush washers, drove around with both the gas cap and the vacuum hose to the shut off, also tried blowing into the shutoff in case it was sticking. I have my lift pump off and am letting it soak in carb cleaner because im rebuilding it in case one of the check valves is no good. Any thoughts on what could be going on ? really kills the useability of the car not being able to shut it off.

What car is this exactly as there is no 300TDT. Is it a station wagon with a turbo? Or could it be a 300D sedan with a turbo? First of all we need to know what it is.

your vacuum valve at the ignition switch is sticking and not allowing the vacuum to bleed off, thus holding the shut off in shut off position
so replace or clean (not with brake cleaner) rubbing alcohol worked for me

i already unhooked the shutoff and tested that, i also blew into it to maybe unstick the shutoff. to tyl604 yeah its a 300td-touring or wagon whichever you prefer

How long of a ride when you say when warm. I am yhinking try doing the same drive without the fuel cap on. You may have a stuck pressure relief valve in the fuel system. When you start it has had time to slowly return ambient pressure to the fuel tank, then after running it creates a vacuum in the fuel system making the fuel delivery system work harder than it should. Just a guess, and a zero cost try to determine the problem. That problem would also be more pronounced with a full tank.

The shutoff operates by vacuum, your ignition switch valve sticking is allowing vacuum to hold the shutoff closed thus the no start.

I have tried driving without my gas cap on and as i said above, i took the vac lines off the shut off on the IP to rule out a sticking ignition valve, i also blew into the line to maybe push it out if it were stuck. The car just needs to be run to temp and then it wont start.

Sorry... but there is a 300TDT. Mine is and I have the owners manual that came with it and calls it that also. Touring Diesel Turbo.

W123-300TDT-Motor/en

Ngarover - right you are. Does it actually have the chrome letters TDT on the outside? Not sure I have ever seen one - but then I have not really looked closely. Still thinking of buying one - a station wagon.

A few things I might check. I have owned the occasional diesel that ran well but was resistant to hot restarts without some glow circuit activity. Just a little was enough. These where the old 1.6 litre volkswagon diesels. The occasional engines involved never seemed to be really tired either. I never attempted to find the cause.

I was also wondering if the injection pump was perhaps so hot that the fuel inside might be thinned down too much in hot soak . Make sure the relief valve is overflowing. The returning fuel cools the injection pump as it carries away heat.

One test would be a small container of vegetable oil as the viscosity remains higher if it eventually got to the point the injection pump was suspect. Now if the car ran bad wvo this pump issue might need some consideration.

Does the rotational speed of the engine seem about the same? Starters can also develop heat soak conditions. Usually the solenoid will not lock in but there can be other issues.

At least in my mind there are many possibilities. Some of my tests are crude but for example I might start a light spray of water directed on the injection pump from a hose and let the engine come up to the problematic temperature. Shut it off and see if it will easily restart say a minute later.

Generally speaking hot restarts have not been a common issue on these 123 engines to the best of my knowledge. . Plus not mentioned that frequently on the site. Since you purchased the car with the problem. You probably have no knowledge if it was a sudden onset issue or one that became worse with time. Make sure the relief fuel overflow is occurring and I suspect it probably is with the new lift pump. Then close off the pump overflow line to verify you do not have a wide open relief valve. Hotter thinned out fuel might see so little return line resistance that no fuel pressure is developed in the base of the injection pump for a hot restart.

Yah trust me its not a common issue, i have searched through so many threads and prettty much no one has this problem. It was sudden onset, car ran great for me for about a month before this issue started. I like the idea of cooling down the pump and pinching the return line to test this issue. I still feel like it is something wit the shut off on the IP, the car is just starving for fuel but once it kicks it ll go. I did do a little wd40 into the intake and it started then ran. I have tried disconnecting the vac source from the shut off, is there something else i should be doing incase its sticking ? I just got home from work and am about to go for a quick spin to heat it up and then try and make her start back up.

If it will start due to WD40 then it is pretty clearly a fuel issue...
but you should pull your glowplugs and ream those holes..
if that does not help... you may need to pull , inspect and clean your precombustion chambers.... they are critical for the dispersion of the fuel into the combustion chamber... they are very small holes drilled radially.... also important is the pintle which breaks up the fuel on the way to those holes... from the injector.... these are at the HEART of the engine working properly... yet are very seldom checked....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

but why would it start right up and run great when cold, and if you can manage to get it to start when hot it will also run great. I have a fuel pressure gauge on the return side of the primary filter so i can see whats happening as i drive. I can get it to start when warm but it involves way too more cranks than i d ever feel comfortable doing far from a battery charger, once it catches the tiniest bit off it goes. I am in new england so when i say cold i mean on 70-85 degrees right now

Knowing sudden onset of the problem for certain is very helpful. Far less of a chance of worn elements in the injection pump being an issue. .

I guess without really knowing that much myself. Technically perhaps the shut off does not like to release when the injection pump is hot? Rather than using the shutoff to stop a hot engine . I might remove the air cleaner and block the air to kill the hot engine. Then see if it will willingly restart after a minute. Tricky test to be certain by interpretation but if engine restarts easily it might indicate a sticking shutoff could be it as you suspect.

Cranking hot have you tried holding the fuel pedal down? It does sound like too little or no fuel being injected when hot. My last thought is I would check the egr system to make sure it is closed when the engine is hot. Initially right after shutoff if it is still on the engine could be flooded with exhaust gas residue. Leaving no oxygen to burn the fuel or not enough. just pulling the vacuum line off and blocking it disables the egr valve if it is in normal condition. Some put a ball bearing in the vacuum line to it but including a plate is better as well.

Disabling the egr exhaust gas recirculation system is a good move anyways. Unless you spend a lot of time running around hugging trees. It could clear this gas enough by sitting for awhile to start again . Pretty long shot but not an impossibility either.

I really do not expect there is much wrong. Just that it may take a little to identify it. Tests to me are almost more helpful in identification of a fault. Or at least many times lead me to the true issue. I kind of eliminated fuel drain back issues of any sort as the problem should be worse the longer it sits. Some kind of air issue is not off the table though either I suspect. Personally if it goes on I would want to study the return fuel out of the injection pump in a clear line for bubbles when very hot.

Anyways do not start pulling your hair out. The car will not start hot if you are bald as well either. Actually I already know what the problem is. It will be the last thing you check. Always seems to work out that way for me.

Last but not least if your memory is still intact. Do you remember if you did anything inside the engine compartment right before the onset of this problem? If by luck you did have another look at it. Even switching a vacuum line accidentally can cause issues.

Have you run a can of diesel purge through it? If injectors are streaming you are not getting atomization required for an easy start. When cold the glow plugs provide the heat required and it fires quickly. Sure sounds like a fuelling issue.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10