Hey folks, new to the diesel end of this forum.

Looking at buying a '95 PSD, my only concern is the truck won't keep running. In the owner's exact words "I got it primed up then lost prime I believe it has an air leak in the system" "I can get it to start if i vacuum prime system it will run then loses prime and cuts off". He also said he recently changed the fuel filter and the truck has a 6 position chip (I have NO IDEA what a 6 position chip is or does, but its a modification he mentioned and I know it has to do with tuning so I figured it could be important).

My first thoughts from what I know about diesels (I had a 2012 Jetta TDI, so, not even close to the same animal) is the truck is losing prime because of a fuel leak. Maybe a hole in a line somewhere OR it has to do with the fuel filter he just installed.

The guy is asking $3500 and it feels like a decent deal to me, but I want to look first before I jump in with both feet, ya know what I mean?

 

Do you know if the mechanical fuel pump has been changed? This is what it sounds like to me, the pump's low stage is not working. These trucks have a 2 stage mechanical fuel pump. The low pressure side draws fuel from the tank, routes it threw the fuel filter back to the high pressure side of the pump. You can check the fuel pressure with a cheap pencil type tire pressure gauge at the schraider valve on the fuel filter bowl. You should get at least 20lbs there WHILE CRANKING the engine. It could be as simple as replacing the fuel pump to get it going. Or for more dollars it can be converted to an electrical delivery fuel system.

 

I'll keep that in mind, two of my friends are thinking its the fuel lines leaking, but a mechanical fuel pump sounds nice and easy, and best of all, cheap!

 

To clarify, he says the truck loses prime while it is running. I don't know if that changes the diag much.

 

I think what Tom said is right on and if you had a small leak in a fuel line you would know it.

 

I don’t know how he is vacuum priming the system.

Even if he could do it, If the hoses had a leak, then the leak would not allow a vacuum prime as it would leak while attempting to prime.

I am also with Tom, sounds like a possible fuel pump. The guy may be pouring fuel into the filter housing then starting it. This would supply the high side with fuel, but it will run out without the low side doing its’ job.

I would dedinitely want to hear it run as his description may not be accurate.

The chip is fairly common. If possible, find out where he got it, and whose tunes are on it

 

About the 6 position chip. Better question is to find out why the owner installed it. Some get them for better towing and / or offroad manners. Some get them to roll coal. And some get them for ego as they want to outrun a Cummins.

Put another way, if the current owner says something like 'Yeah, whenever I see a (pick a favorite hater vehicle), I flip the switch, she runs like a scalded dog and we spank that moron', this indicates that the truck was a toy, beat-on, and now there is no clue how to fix it. So, that stalling issue could turn into the iceberg's tip.

Related, using a chip to change tunes should also have supporting mods and the bare minimum is EGT. If there is no EGT, I'd get ready for either a repair pit or turning this into a donor truck.

Granted that $3,500 might seem reasonable, but it could also prove just a small deposit toward near term repair costs.

 

X2 on this one.

 

Does the "Fuel Filter" light in the dash come on when the engine is running? That light is connected to a vacuum switch on the vacuum side of the fuel system at the fuel bowl, ie, on the low-pressure side of the mechanical fuel pump which draws fuel under vacuum from the fuel tanks to the engine filter. If that light comes on, it is indicating there is excessive vacuum in the fuel system, and this usually results from an obstruction in the system: a broken and clogged fuel pickup strainer in the fuel tank, excessive sediment clogging the fuel line, microbes or ice crystals creating excessive resistance, etc.

 

Jerry, Jerry, Jerry! You don't want that pile of rust! Just give me his number and keep looking...I've taken care of 'his kind' before!...

LOL! You are in the right place! What does "lose Prime Mean"? Is it a 'California/Cali model'? Does the filter housing run dry? Lot's of "What does 'X' Mean"? It could be be a CPS or any number of things. I will say these guys here have seen it all and welcome a challenge. They will see you through, no doubt in my mind. If I hadn't found THIS EXACT Forum way back when, I would've sold my truck loooong ago! They don't treat you bad or like a child...everyones 'expertise' level differs. I had a 09 Jetta TDI and currently have a 15 Jetta TDI and you are right...completely different animals...except what they eat. If you are close by and going to look at the the truck...I would ask what exactly to look at...I'd be willing to bet depending on day and time...someone may even FaceTime with you while you are there to help. This forum is the BEST "Manual" you will ever have! Good luck and stick with it

 

Stock fuel system is crap, really it is not worth screwing with it.

Anyway, $3500 I guess but bet on putting another $3500 into it at least so it is solid unless you have stacks of receipts.