Bought the Durametric but I need help understanding the numbers

[tholyoak]

Make sure your vacuum to the fuel pres reg (FPR) is routed as illustrated in Wayne's diagram. The lines in green must always see vacuum and thus are routed with a 1 way check valve (H) and a reservoir (F). The vacuum supply to the FPR must change with engine vacuum (load) and is routed directly to the nipple on the intake boot (B) as shown in blue in Wayne's picture. The vacuum reduces the fuel pressure at low load (idle) (3.3 bar =/- 0.2) and the loss of this signal as load increases results in an increase in the fuel pressure to 3.8 bar (+/- 0.2). In addition to pressure, check the pump delivery rate as well. It should be at least 850 mL in 30 seconds.

-Todd

[Dale_K]

Thank you Todd. I had a little brainstorm while taking my exercise walk just now and thinking about the diagram. All this time I've ruled out vacuum line leaks since nothing showed up in those places during the smoke test. Hells bells, there's no way the smoke test can reach the vacuum lines because the checkvalves are going to prevent the backwards flow of smoke.

I'm going to look at the car right now and I'll report back.

[Dale_K]

Alas, no joy. This was the first time I actually hoped to find a problem on my car after guessing it might be a fuel pressure issue. My fuel pressure regulator line looked just like the diagram. It didn't have a check valve (just like the diagram) and there was a little lump about an inch from the end at the manifold, which I assume is a telltale to let you know how far to push it in.

I started the car with the line disconnected at the regulator and a golf tee stuck in the open end of the rubber elbow. It definitely had some vacuum. I hooked up my MightyVac to the port on the regulator and it will hold a vacuum so maybe the pressure regulator is OK. I won't know for sure until I measure the fuel pressure and I'm waiting for the test port cap before I take off the one on the car. If the pressure checks out I'll replace the MAF sensor and hope for the best.

[Wayne 962]

I think the mass airflow sensor is your best bet at this point indeed.

Wayne

[Dale_K]

Update and I hope closure to this thread. I installed a new MAF sensor today and test drove the car for 30 miles at moderate speeds. The fuel trim readings were very different and appear to be in the normal range.

Adaptation range 2 FRA bank 1 = 1.00
Adaptation range 1 RKAT bank 1 = 0.42
Adaptation range 2 FRA bank 2 = .98
Adaptation range 1 RKAT bank 1 = 0.56

If I'm interpreting these correctly the "FRA" or higher load readings are very nearly perfect and the "RKAT" or low load readings show a slightly lean condition, which makes a lot more sense than the numbers in my previous posts, which were massively lean at high loads and rich at low loads.

Thanks for the advice and information.

[Wayne 962]

Despite all the complicated information one may get out of the diagnostic tools, I continued to find these cars very easy to diagnose and fix. It would seem that 95% of the time, the problem is a vacuum leak or a dirty / worn out mass air flow sensor (MAF).

-Wayne