Diesel woes, again? I hope not.

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Last week, I got an inquiry on Facebook regarding a Pajero FieldMaster. The problem was his top speed was only 120 kilometers per hour and the owner of the Paj was asking if I was willing to help tune his Paj. As a routine for me, I try and ask about the service history of the Paj. Mileage, service done, what fuel is being used, tire size, is it a second-hand car, does he have a regular mechanic who services the Paj… while corresponding with him, he said he already had the fuel tank drained and cleaned. Changed the fuel filters, oil change, stock tires, used diesel fuel additives and almost a year ago had the injection pump rebuilt and changed the injector nozzles. Reason for the rebuild, black smoke and they said the oil seal of the pump were leaking and it was having a hard time starting in the morning. And before doing this, the Paj was hitting 140 kph. Hmmm… so I asked him what brand were the nozzles used. He said Denso. Hmmm… ok then I asked how much did he pay for the set of nozzles. He said around P4,000 for a set. Hmmm… possible red flag here. Why?

From experience, the original nozzles installed for the 4M40 is by Zexel. Yes, Denso may have a part that can fit the 4M40 but OEM (original equipment manufacturer) was Zexel. Stick with what came with it. If your engine came original from the factory using Denso, then stick with Denso. Now, the price… a set of original nozzles can set you back P7,000 to P10,000 a set. A shop may say it can offer a replacement set for a cheaper price. How’s that? What some shops do is they would use a nozzle for another engine and make it work for another engine. The set for the 4M40 is a bit steep. But the ones for the 4D56 is slightly cheaper. Yes, it would fit, but what would be the difference? The spray pattern. Different diesel engines have different needs. The spray pattern can be wide or narrow. If you look at an injector nozzle, the area where the fuel comes out, where the pintle is, the area is slightly dished. These differ from nozzle to nozzle. This determines the spray pattern of the fuel as it exits the nozzle. That’s why when you look at the body of a nozzle, there is an identification number specific for a certain engine. The wrong spray pattern can make the atomized fuel pool in specific areas in the chamber or not distribute the fuel evenly. This can cause knocking or detonation. Power output can be compromised. Its worse if the shop offers you a fake set of nozzles. All kinds of problems can arise. Then they would say that the engine needs a rebuild. I have seen engines with “brand new” nozzles and the owner complains that it doesn’t run a good as before. When we take a peak at the nozzles, it’s not the same spec as the original ones. I loaned the owner a set of reconditioned nozzles correct for his engine and it even performed better.

Shops who do such things give diesel cars a bad reputation. I would hear of owners selling their diesel-powered cars in exchange for a gas-powered one. For the owner of the Paj who I am corresponding with, he is yet to pass by and let me take a peek at his ride. Hopefully, it would be a simple fix as he has already mentioned that he has spent quite a bit for his ride and he is considering selling his Paj. Hopefully, we can fine-tune his ride so he can reconsider not selling it. If you have a tech question to ask, please email me at drdavemech@gmail.com.

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