DIESEL TECH FAQs

INJECTORS FOR OLD  F-350 7.3L

Q: My old ’92 F-350 7.3L IDI work truck has started blowing white smoke  when pulling grades. The engine has 50,000 miles on a rebuild that included rebuilt injectors. What would be my best route on finding good injectors? They seem to be a little hard to find.  

A: Finding injectors for the old Ford IDI Navistar 7.3s isn’t that difficult whether shopping on eBay, or brick-and-mortar diesel fuel-injection shops like Mobile Diesel Service. It just depends on how much you’re willing to pay and how much trust you put in the seller. We trust Industrial Injection  OEM Stanadyne injectors for the non-turbo 7.3Ls.  American-made remans might be a good choice if you can't afford to drop $500 or so on a set as long as the seller has a good warranty coverage policy. Either way, our diesel repair shop parts guys can help you out.

QUESTIONABLE 2017 F-TANK READING

Q: Why the fuel readout in my 2017 Ford F-250 Power Stroke reads empty when there’s still 8 or 9 gallons left in the 34-gallon tank? 

A: Our understanding is Ford uses the diesel in the tank to keep the in-tank lift pump cool. It apparently takes five gallons of reserve fuel to do so in the 34-gallon tank. So in essence, the “useable” size of the tank is actually only about 29 gallons. The other concern is anytime air is sucked into the fuel system as a result of the fuel in the tank being too low, you risk doing damage to the high-pressure fuel injection pump. When newer diesels get down to a ¼-tank, it’s time to fill-up. As for recalibration, Ford issued a TSB ( May 31, 2017) on this very issue.  It covers 2017 F-250/350/450 built on or before December 1, 2016. The TSB fix? Replace the 34-gallon fuel tank and fuel level sending unit. That apparently means Ford did some sort of tank re-design that requires less fuel to keep the lift pump cool—or relocated/re-designed the “new” fuel pump to sit lower in the tank. Our Mobile Diesel Service deisel engine diesel truck shop mechanics suggest  if you are having the fuel tank/sender replaced,  install an aftermarket FASS Titanium Series lift pump at the same time. It'll save you money becasue the lift pump also requires dropping the 34-gallon Ford fuel tank and the removal of the factory in-tank lift pump. We would be happy to assist you in parts and installation if needed.

6.4L SLOW TO BOOST

Q: My 2010 F-250 6.4L has slowly been taking longer and longer to build boost, and now boost doesn't start coming on until around 2,500rpm. I've replaced the fuel filters, checked fuel pressures, replaced the EGT and several other sensors, had the DPF cleaned, and replaced the thermostats. Still, it feel like the truck keeps going into "limp" mode. No codes are showing up, either. Do I have a failed turbo?

A:  So, without a computer to talk to the PCM, if you are trying to diagnose an "air management issue," i.e., boost problem on a 6.4, Step #1 is to verify the VGT arm is moving when the ignition key is placed in the "on" position. When the key is cycled back "off" the VGT arm should return to the rested position. The next step if the VGT arm does self-check, is to check for  any air intake boost leaks or exhaust leaks to the turbo. Step #3: Hook up the PCM to a computer and verify KOEO that the Exhaust Pressure sensor is reading correctly (Barometric pressure) and it changes with the engine running. Step #4 : If the sensor is reading correctly is to remove the air crossover that feeds compressed air from the low pressure (larger turbo) to high pressure (smaller) turbos and inspect it and the two turbos. We've seen cracked up-pipes cause this, and on very rare occasions a cleanly broken impeller shaft on the high-pressure turbo. Like any diesel issue, you have to go down a diagnostic checklist to find the real issue.  

BIG LML FUEL LEAK

Q: Fuel started pouring down the rear of my 2015 Duramax just as I was starting to leave home. Smelled fuel, and there's a wet trail behind the truck. Opened the hood and finally traced the source of the leak to what appears to be a curvy black rubber hose that connects to the driver-side fuel rail. What does the hose do and is it difficult to repair? Truck is out of warranty. 

A: The hose you are talking about connected to the fuel rail is the low-pressure fuel return hose. Rubber hoses in the engine valley, such as this one, are prone failure because the rubber gets weak from the constant heat cycles they are exposed to being so close to the turbo-and sitting on top of the block. Some DIYers use a six-inch piece of bulk fuel line hose to make the repair. That’s not a good idea on hoses where they are formed to make sharp bends. For the hose in question we suggest using the GM replacement part (#12645582) because it’s formed to fit into the tight confines, whereas regular fuel line hose could kink and collapse when it gets very hot. Cost for the GM hose should be about $20. The fix does require removal of the EGR valve and probably unbolting the AC compressor in order to get to the fuel return hose clamps. If you can easily get to any other rubber hoses in that area, now would be a good time to replace them using bulk fuel line hose where applicable.  We do these repairs all the time here at Mobile Diesel Service. If you don't want to tackle it yourself, give us a call.  

NEED BETTER MILEAGE

Q:  I have a 2011 6.6L Duramax. I have been checking the Edge insight Pro CTS 2 programmer. They say you can up mileage by 2-3 mpg. Have you tested these? I want more in mpg than a ton of power. I only tow about 7000 pounds. 

A: We've installed a lot of Edge Prodcuts programemrs here at Mobile Disel Service.  What we've seen is if the driver is lighht-footed, there is a gain in fuel economy. However, fuel economy dropped more than it did in stock mode whenever the new-found power was called upon. That’s going to be the general result of just about any “economy tune” on the market, regardless of brand. The reason is simple: Fuel and timing are the primary elements of building power in a diesel. Aftermarket programmers, such as those at Edge Products, spend thousands of hours using dynos and computers to manipulate fuel-injector pulse widths, making them longer or shorter than stock programming at any point along the power curve, to suit a specific goal. They pay very close attention to the fuel-to-power ratio, or Brake Specific Fuel Consumption (BSFC) and exhaust gas temperatures (EGTs). When BSFC reaches a point of diminishing return, or EGTs endanger engine longevity, the programmers back down the amount of fuel and adjust timing before moving on to the next point in the rpm band that they want to change. What many programmers do to give a boost in fuel economy over stock is targeting light-throttle, steady-state driving situations, such as you find cruising down the highway. In those instances, they typically shorten the injector pulse width (less fuel) and adjust timing as much as possible during that specific point in throttle position, engine rpm and vehicle speed. Hence the potential “gain” in mpg over factory.  Drop by the Mobile Diesel Service truck repair shop and talk to our guys working the parts counter for more details about programmers. 

WIPED OUT CP-4 INJECTION PUMP

Q: My truck just shutdown and I had it towed into your shop. The tech said he thought it was a grenaded injection pump. He was correct. When they removed  the pump and took it apart, the little crankshaft and pistons that do all the work inside the pump were in pieces.  What caused it to fail?

A: The Bosch CP4 pump design has been a bit of a problem in both big rigs and GM diesel pickups. We've seen several of both come through our diesel engine repair shop here at Mobile Diesel Service over the past couple years. So far no one has been able to clearly define why they come apart. What we do know if when it happens, the debris from the failed components are flushed through the entire fuel system from tank to injectors. It's a very time consuming and expensive repair because the entire fuel system has to be flushed clean , injectors and pump replaced, and sometimes other components need to be repaired or replaced. Keep the fuel clean, filters changed, and consider using a fuel additive/conditioner. Water and dirt are sure killers of today's injection pumps!