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Topic: Follow up ? To: on for service, won't start. (Read 742 times) previous topic - next topic

Follow up ? To: on for service, won't start.

Ok,  yesterday's non-start comes down to a bad fuel filter seal and an air bound injector pump.
I would have thought that the injector pump would deliver enough pressure to clear itself of air (once it got fuel sans air) without needing to bleed at the injectors as it would have to overcome engine cylinder compression.  Cummins is direct inject, no?
Apparently not.
Any good explanation as to why this happened?

Re: Follow up ? To: on for service, won't start.

Reply #1 –
Quote from: Moby –
Ok,  yesterday's non-start comes down to a bad fuel filter seal and an air bound injector pump.
I would have thought that the injector pump would deliver enough pressure to clear itself of air (once it got fuel sans air) without needing to bleed at the injectors as it would have to overcome engine cylinder compression.  Cummins is direct inject, no?
Apparently not.
Any good explanation as to why this happened?
The injector pump moves very little fuel per stroke.
The line from the pump to the injector is at system pressure.
Direct injection means directly into the combustion chamber.  Some engines use a pre-combustion chamber.

Just for fun:  The injector sprays into a combustion chamber built into the piston so injector timing really needs to be spot on.

Re: Follow up ? To: on for service, won't start.

Reply #2 –
Direct or indirect injection has nothing to do with it. You are not overcoming engine cylinder compression. Cracking just one pipe at the injector allows air to escape from the pump. Remember, air is compressible so with all the lines tight, the pump just compresses air. The main injection pump achieves about 3000 psi of diesel at the injector. It can't compress air to 3000 psi so the injectors get no fuel as well as the pistons in the injection pump.

Using a priming pump on the other hand pushes all the air ahead of the diesel fuel, fills the filters, pushes all the air out of the injection pump and out through the relief valve that is usually mounted on the side of the main injection. The air returns to the fuel tank and nothing is left in the fuel system but diesel fuel.

The hand primer pump is easy at first as it's pushing air ahead of the fuel and when the relief valve opens the air quickly goes into the fuel return line. When nothing is left but fuel in the system, the hand pump gets a bit harder to pump as the diesel is not compressible (for all practical purposes).

Unless you have a CAT without a return line, use the hand pump or install a electric pump as I posted from Tom Hall's site. Then no one with write a post on why their diesel won't start after changing filters. As you have seen, many shops don't have the concept down either.

Installing filters is just no big deal. Anyone can do it. The filter unscrews, you put a little diesel on the rubber gasket and tighten it as the instructions on the box or filter state. If you puncture the secondary with a punch, you can drain it without spilling a drop. If you have an electric pump, you can just tighten the filters and turn on the pump. You do have to purchase an electric pump that puts out more pressure than the injection relief valve but the specs are on the web site you buy the pump from. If the relief valve is spring loaded for 20 psi, you would need an electric pump that puts out more than 20 psi. If less than that, you would have to crack a fitting on the injection pump or loosen the relief valve a half turn.

You could coast down a hill and put it in second get to get the air out. Oh, that's right, we have automatics.

Pierce

Re: Follow up ? To: on for service, won't start.

Reply #3 –
I only use engine oil to lube filter seals.

Re: Follow up ? To: on for service, won't start.

Reply #4 –
Quote from: Pierce & Gaylie Stewart –

The hand primer pump is easy at first as it's pushing air ahead of the fuel and when the relief valve opens the air quickly goes into the fuel return line. When nothing is left but fuel in the system, the hand pump gets a bit harder to pump as the diesel is not compressible (for all practical purposes).

You could coast down a hill and put it in second get to get the air out. Oh, that's right, we have automatics.

Pierce

You were always the teacher's pet weren't you Pierce.

Have to be a long hill.

Re: Follow up ? To: on for service, won't start.

Reply #5 –
The 3208 cats appear to have a return line that carries a whopping peak 8 gallons an HOUR. I changed one filter at a time without filling it. Hand pumped it up, started it right up without issues other than a couple of small rpm hickups once running and let it run ten minutes, same for the secondary filter. Hand pumping causes really big bubbles or voids to turn into really small bubbles or voids that the 3208 engine can endure, hick up and tolerate. Love the really simple, forgiving, big displacement mechanical injection 10.4 liter 3208 cat. Only downside seems to be it's only a 350k mile motor that costs $7k long block and has to come out the bottom if necessary.
 

Re: Follow up ? To: on for service, won't start.

Reply #6 –
OPP,

I was thinking about my previous post on adding Tom Halls electric pump but realized that not many are going to be able to do that so thought I would do some research on the issue. I've come up with a primary filter housing that comes with a hand priming pump plus the S3202 primary filter and plastic bowl with the drain. The S3202 30 micron filter is the one many Foretravels use including Detroits, 5.9/8.3 Cummins and CATs. This is exactly like our stock housing but has the pump on the top. You just use the palm of your hand to pump the fuel. At $50 delivered, you could order two and keep one for a spare. 3/8" NPT Diesel Fuel Filter Water Seperator Hand Primer Pump HANLV 30 Micron...

Years ago, Mercedes moved the priming pump from the lift pump that was mounted on the side of the main injection pump up to the filter. The original worked well but you had to turn the top a few revolutions and then pump. A little difficult if greasy and also if the engine is hot. The new location uses the exact same type of pump with only the palm/heel of your hand needed to pump it.

While I'm at it, when changing the generator secondary fuel filter, make sure to open the "T" handled valve while bleeding they system. This is done in some 10K generators by holding the start switch in the glow position as this also activates the electric fuel pump. Without opening the valve, the electric pump does not generate enough pressure to push air past the spring loaded fuel return valve so the system won't bleed the air out. You will notice when the little valve is open, how easily the electric pump evacuates all the air from the fuel system. Some 10K generators don't have the little valve so a fuel line will have to be opened to let the air out. I've seen posts on other forums recommending the valve be left partially open for best operation. If it runs better with the valve partially open, it's because the generator fuel supply line or clamp is allowing air into the system.

OPP, while your engine may have needed overhaul at 350,000, this the B-50 mileage for both 5.9 and 8.3 Cummins. This means 50% will need overhaul at this mileage. Others may go two or three times further before needing overhaul. I see the new Volvo and Detroit have a B-50 mileage of 1.3 to 1.5 million miles but this is in the trucking industry where the engine sees thousands of miles a month and has computer controlled maintenance as well as a shut down timers.

Seven best filters with hand pumps on the housing: Top 7 Best fuel filter primer pumps - WhyWeLikeThis Make Product Search Better

Most diesels return a big percentage of the fuel back to the fuel tank. One of the reasons to keep the tank fairly full in hot weather as our tank gets too hot to keep your hand on it after a few hours driving. I think Brett put a cooler on the return line on his.

Pierce