Starting Issues - Any Ideas?

[matkinson13]

Hey y'all -

Fern is having trouble starting if she hasn't been driven in a day or two. I know it's getting cooler so I cycle the glow plugs a few times, then try to start her. She'll start, run for a second or two, then quit. The happens a few times in a row.
The only way I can get her to start and actually run is to press the diesel pedal. Once she warms up (like out running errands), she re-starts every time. It's just the first start of the day that's the problem.

It's like she loses prime at the injection pump or something. Any suggestions on where to start looking for a fix?

Thanks!

[tyl604]

My '81 300SD used to do this. Had the valves adjusted and problem went away. Were way too tight. Would hardly run until the engine got warm.

Just a thought.

[Sugar Bear]

Yes to a valve adjustment.

How old is the fuel? Did it get a lot colder while still having summer blend fuel in the tank?

Try listening for the glow plug relay opening and then starting it immediately vs. waiting for the light to go out. The light will go out quite a bit before the relay opens.

[matkinson13]

Copy on the valve adjustment. I'll add it to the list, along with checking on the glow plug relay.

Summer/winter fuel issue is a possibility, the diesel's been in there a bit. But it's still relatively warm here in AL. Cooling, but not cold.

Thanks for the ideas - plenty to learn about our girl.

[Diesel911]

I am going to look at it from the fuel perspective and the loss of prime.

There is rebuilt kits for the fuel supply lift pump.

One way to test for that is pic a cold day that you would normally have trouble starting and start pumping on the hand primer a lot of times. If is starts up normally after that there is a good chance the fuel supply lift pump is losing prime.

If you are leaking fuel around the hand primer while you are pumping that can be an area that allows air into the fuel and also a loss of prime. That would need to be replaced.

On the back side of the fuel injection pump facing the engine block is what looks like a normal banjo bolt but there is a valve inside of it. The fuel pressure relief/overflow valve is what controls the fuel feed pressure inside of the fuel injection pump.

If you have the type that can be taken apart, you can remove the spring and ball bearing that is the valve and stretch the spring to a 27mm free length. Or buy a whole other valve.

When the sprig is too compressed it does not hold the fuel pressure as it should be especially at cranking speeds.

In the picture is one of the types that can be taken apart. Others have a plug that screws in flush to the top of the valve but has a screwdriver slot.

Some cannot be taken apart and have a ball bearing pressed into it.

[vstech]

If you are parking on an incline, park the other way and see if the problem stops.
Fuel hose brittleness can allow fuel to siphon back to the tank when parked nose uphill.
If parked level, try raising the rear at night.
All it takes is for the primary filter to get a bit of air, and starting can be difficult.

Adjusting the valves REGULARLY is key to good starting on these motors.
If its been a while, adjust them twice.

[Gofast1976]

Did you get the valve adjusted?

[matkinson13]

Hmmm. I do park her on an incline so will try parking level or tail up. Interesting.

And no, I haven't had time to adjust the valves. We traveled to Thanksgiving with family in LA and daughter is getting married in two weeks. But will get on it, you know, when I get free time. So probably in 2026 sometime. Ha!

I do appreciate the suggestions and ideas. Thanks, y'all.

[matkinson13]

Follow-up time...

Finally adjusted the valves and she runs a LOT smoother with more power (according to my butt dyno anyway). Intake valves were pretty spot-on, but exhaust valves were way off. Now she's got a peppier feel overall...as much as a 40 year old girl with 321K on the clock can have. She doesn't choke on hills now and I can mostly keep up with traffic.

About starting issues...she's been parked level for a while but still won't start unless the accelerator is pressed down completely. Once warm (like running errands), she starts with no issues. Glow plug relay & system are next to check.

Thanks for your advice!

[evranch]

Same issue despite valves being adjusted? Hmm.

Does it cough a significant amount of smoke of any colour on startup (with pedal or without)? Does it sound like the engine is firing on all cylinders or does it lope and sputter? You're starting with the pedal on the mat, so does it surge up to speed quickly once it catches or does it struggle to get going?

[matkinson13]

I'll check but I don't remember a huge cloud of smoke on startup. It does sputter and lope a bit until warm and won't start/run until I press (and stay on) the pedal. But with foot on the pedal, it runs. If I give it a minute or so of pedal down to get it warm, then shift to reverse (to back out), it might run for a minute and then die again.
I'm wondering if this isn't a combination of a few issues. Such as: valves out of adjustment (now fixed) and also glow plugs possibly not working. I still have to check the relay to see if it's working.

EDIT: My fuel return hoses (off the injectors) are old and cracked and leaky, so that may also contribute. I've got new hoses on the way, so can rule them out soon.

More to follow...

[evranch]

I would definitely check glow plugs individually as well as the relay.

With only a couple working it will start on those cylinders, and then you need to keep the speed up enough to keep the un-glowed cylinders lit until they warm up.

Fuel return hoses don't really matter much for operation as they just transport leakage back to the pump. I replaced mine when I changed my glows, and they all still have air bubbles in them that rock back and forth.

[rrgrassi]

Have you checked the hand primer pump? My 82 did that. Primer pump was allowing air in.

[matkinson13]

You know, I haven't checked the primer pump.

Is it supposed to screw down closed? Thought I saw that somewhere but I was never able to get it to screw down, if so. The handle just turns and turns. It's also likely user error.