Detroit 14 L DDEC 5 - no power on hills, after inframe.

This is from another Diesel forum.


"...........There are 2 holes at the back of the head. 1 is supply- 3/8 pipe coming from the fuel filters. The other is 3/8 pipe also and the first thing you see is a fitting. This is a special restricted fitting of R80. This fitting basically controls fuel flow and allows the fuel pump to maintain a pressure in the fuel rails. 15 min. at idle and about 65 at n/l speed. Thats all there is to it. Period. The check valve has a purpose to maintain the fuel in the cylinder head after shutdown. The DDA check valve requires very little pressure to unseat the spring. ANy excessive pressure to open a generic valve will cause a loss of fuel flow and could possibly cause low HP. The 'R' fittings is a 90* elbo then the check valve screws into that. ALL DDEC 1,2,3,4 series use this system. The DDEC 5 uses a different system. Most FL trucks have the fitting next to the block. Some other truck manufactures have an 18" pigtail then the check valve. It is a PITA to remove the side fender and crawl in that small space to have axcess to the fuel system. Better to remove the rocker cover,jakes,rockers and morph yourself over the top. Either way is a PITA......"


This gentleman is talking about the check valve, so I went to the dealer to purchase the valve and I asked them for the restricted fitting and they said: Your engine does not use one, you have only check valve. This means that only DDEC 1, 2, 3, 4 use check valve and restricted fitting and DDEC-5 uses only a check valve, which maybe doing both: restricts (for fuel pressure) and not letting the fuel in the cylinder head to go back in the tanks, when the engine is shutdown.

 

It looks pretty solid. I choosed this one, because all the other gauges for fuel pressure were intended to use on gasoline engines and only read up to 10 psi.

A tool specifically made for the diesel fuel pressure, could cost maybe $ 300-500.

 

I just want to make closure on the problem. First off - the. DDEC-5 fuel pressure is not like on DDEC - 1,2,3,4. The max fuel pressure on DDEC- 5 is 35 psi. At idle about 15 psi. This engine does not use restricted orifice - only check/regulator valve. The EGR is driven by oil not air, so you have only one VPOD. It turned out, I have a complex problem: low fuel pressure - fixed by replacing the check/regulator valve, VPOD working only 50% - put a new one. The turbo shaft, moved by actuator was leaking only on top position, that is why was difficult to notice. So I need a new turbo.

I will report later if this finally fixed the power on hills problem.

 

With DDDL 6.5 and air gauge on the turbo actuator.

 

For the record: I need a new turbo, but I am still running with the old one.... my MPG is 6.5, with the new turbo I should get MPG 7-7.5