1997 patrol rd28 engine with cold start problems

[Jr1937]

Hi everyone, appreciate some advice re an old mates 97 2.8 turbo patrol. The metal plate in the engine shows it has an rd28 engine. It is having issues with cold starts, runs like a dog and blows grey/white smoke. He hasn't a lot of cash to fix it, so I decided the help him out. From all the blogs I have seen, the glow plugs could be the issue. Also it has the two rail system for the plugs. The plugs 4-6 act as the after glow system and stay on to keep the engine warm as the water temp increases, via a sensor in the back RHS of the engine. I managed to determine that most of the plugs were dead. I found him some tridon brand plugs from repco for about $35 each, compared to the $120 Nissan were after. Replaced all the plugs making sure the correct ones were installed 1-3 and 4-6, as they are different. Used some anti seize on the threads before installing. Cleaned all rail surfaces and reinstalled the double rail system. Checked power on the main rail and this has 12 or so volts and basically goes out after the light on the dash goes out. The light on the dash then flashes, which I am not sure is normal. Appears the first relay under the metal cover near the battery is working, can here it open and close. There is another relay next to it, which I presume is the afterglow relay. Tested the second rail and there is next to no voltage there. Suspect it could be that relay which may have passed its use by date. Also checked the connection at the water temp sender by removing a small clip to take the plus off. All looks ok there. I also noticed there are three blue plug in units near the fuse box, kick panel near drivers foot. Top and second seem to get a bit warm. Not sure if they are the issue either. Be grateful if anyone has experienced anything like this with their 97 rd28 patrol

[Yendor]

If the glow plug light is flashing there's a problem within the glow plug circuit. During the second stage there should be around 12 volts on the small rail and around 6 volts on the main rail. It's more then likely the second stage relay as you have expected (the relay with 5 wires going to it).

[Jr1937]

Thanks Yendor. Is there a way to check the 2nd relay, which looks slightly larger than the main one? Presume that the second relay provides the 12v to the small rail and the 6v to the other longer rail.

[Yendor]

The 2nd relay is a change over relay. The first relay is just a standard one.

When the 2nd relay is switched on. The 2 lots of glow plugs go from being in parallel to being in series. So 12 volts goes in on the short rail current passes through the rear set of glow plug and then through the front set of glow plugs via the long rail. This is why there should be around 6 volts on the long rail.

At the 2nd stage relay you should have 12 volts on the Green with a Red trace wire and large White with a Red trace wire. When the 2nd stage relay switches on you should have 12 volts in the large Red wire. The other end of this Red wire connects to the small rail.

[Yendor]

Here's how to test the relays.

[Jr1937]

Thanks again Yendor. I will give that a try and see what the test reveals for both the relays. Appreciate your help.

[Jr1937]

Hi Yendor, I managed to pull the two relays out from under the metal cover near the battery, and the best way to do that is not with a screwdriver but small socket set due to the location of some of the screws holding them on to the frame. I unplugged both and tested relay 1, testing the two terminals in the above diagram. The ohm meter went to zero and then ended up say approx 13.74 as a reading, in other words, it didn't stay on zero. I then tested the second larger relay, again with the terminals mentioned above and revived no result from the multimeter. It basically read 0L regardless of the setting I placed it on. This is a multimeter, which is a professional one with an auto range setting. I then tried testing terminals one and two on the second relay and that gave me a result similar to number one with the final number sitting around the 24 mark. To me, this indicates relay two does not have continuity and thus could be faulty. Not sure about number 1 though with the end reading. What do you think?