The K-Jet test kit arrived last weekend, so I got a chance to do some testing with it.

I took the laptop with the service manual on it out to the garage, but decided to test the cold start valve before testing the pressure regulator. Mark, who has been helping me out with diagnosing the K-jet, gave me some good instructions on testing the CSV, I also found a good article here: http://www.tmproductions.com/repairs-and-maintenance-blog/2013/8/4/checking-mechanical-advance-and-properly-cleaning-the-tank. The short version of this is to connect the connector from the idle motor to the cold start valve, bypass the RPM relay and crank the engine. If the CSV is working there will be a squirt of fuel.

I got the wife to crank the engine while I held the CSV in the top of an empty acetone bottle. There was indeed a very strong spray of fuel, so it looks like this is working. I didn’t think to grab a photo, so I have borrowed one from that article to show what the CSV looks like.

Cold Start Valve

Cold Start Valve

One thing that has concerned me however, while browsing the DeLorean tech page about the CSV, I found this information:

CAUTION: The connector on the Thermo Time Switch (TTS) is keyed so that the wiring plug will only go on it one way. If the outer shell of the connector is damaged, the plug can be inserted the wrong way. This will immediately destroy the TTS.

The thermo time switch screws into a hole in the thermostat housing. The shell of mine is damaged so I have tried plugging it in both ways, which means I will need to replace this.

Moving on to the Cold Start Regulator testing, I opened the service manual on my laptop to the same pages mentioned in my previous post. My kit has the valve to the side of the gauge and is a 2 position valve though, unlike the diagram which uses a 3 way valve directly attached to the gauge. I found a youtube video here which explains how to connect the kit. Using this info along with some advice from Mark, I updated the diagram and have included it below for anyone else who wants to test their regulator.

The results of the test were that both sides of the regulator were showing 6.5 bar. The primary pressure, with the valve closed, should be around 5.2 bar hot or cold. Cold control pressure should be around 1.5 bar slowly increasing over five mins to around 3.5 bar, so it sounds like the pressure regulator is faulty,

I also think there may be a blocked return line to the tank, I have noticed the fuel pump is very noisy (it’s brand new) and there isn’t a lot of fuel that comes back to the tank. When I had the issue with the broken return line on the fuel pump, I had the return hose just stuck in a coke bottle. Even after the engine had been running for a few minutes, the amount of fuel that came back wasn’t enough to fill all the bumps in the bottom of the bottle. I thought this was strange at the time, but figured perhaps it was because it wasn’t actually connected to the return line of the pump, there wasn’t enough pressure.

While doing this diagnoses, Mark suggested pulling the primary pressure regulator (PPR) out of the fuel distributor, and seeing how many shims are on the pin. More shims = more pressure. I pulled the PPR out, removed a shim and tested again. Once again both readings were 6.5 bar.

So at this stage It looks like I need to replace the Pressure regulator, and find the return line blockage.