Tried to use injector cleaner tool at the schrader valve Topic is solved

Post by **800artfreed** » 08 Nov 2019, 10:34

I have an external fuel injector cleaner tool. It is the one that uses air pressure to force cleaner into the injectors through the fuel rail while running the engine. You have to remove the fuel pump relay. I successfully did this on my 1999 S70-GLT non-return fuel system but the 1998 is a return style fuel system. The procedure is to set up the air pressure at less than the fuel pump pressure to prevent the cleaner from being forced back to the fuel tank. I used 40 psi at the cleaner connected to the schrader valve.

Unlike the 1999, on the 98 I heard a strange vibrating (moaning) noise and the car did not run. BTW because of the cable based throttle mechanism on the 98 it is more difficult to attach an adapter to the schrader valve (90 degree connector would be helpful). I took out the valve core and clamped an open ended fuel hose adapter line in my kit to the schrader valve allow the hose to clear the throttle cable bracket.

When the engine did not run I put everything back together. When I went to empty to injector cleaner container it was EMPTY! The strange noise I heard was the cleaning fluid being pushed back through the return line and fuel pressure regulator!

Does anyone know what the fuel rail pressure is at idle on a 1998 S70-T5? Or does anyone have other hints on using this type of tool on a 1998? It worked great on the 1999 S70-GLT. Just wish it was as easy on the 1998.

Post by **bmdubya1198** » 08 Nov 2019, 15:57

Hmm... I must admit, I've never heard of one of these injector cleaners. Interesting.

Rail pressure on a '98 should be around 43 PSI, if the information I've seen is correct.

Post by **misha** » 08 Nov 2019, 16:12

It is correct.
-43.5psi on 1st prime without starting the engine
-at idle ...everything around 35psi is acceptable
-43.5 psi at WOT
For FPR at fuel rail (M4.3,LH 3.2 jetronic).

M4.4 management,according to Volvo,must have a constant 43.5psi all the time.
It have FPR near the fuel filter and just fuel pressure damper at fuel rail.

Post by **800artfreed** » 09 Nov 2019, 11:30

Thanks for the info. I will run a test with the cleaning machine hooked up to see what it shows as the operating pressure at idle on the rail. Then I will set the air pressure supply for 5psi lower then that. I will use gasoline to test operations so as to not waste another $12 bottle of cleaner. If that works I will do the cleaning process with the injector cleaning chemical.

Does the return line have a soft rubber section that can be clamped shut before the FPR?

Today the temperature is in the 30s so I will try something tomorrow when it's a bit warmer. Cheers.

Post by **800artfreed** » 09 Nov 2019, 11:34

I reread misha's post. Thanks for the information. I believe the critical information is at idle the rail pressure is only 35psi. I was setup at 40psi. So I can see that with the vacuum levels applied to the FPR it opened up and allowed all the cleaner to go back to the tank. As I posted above I will run some tests and report back. Thanks again.

Post by **misha** » 09 Nov 2019, 16:35

'97 & '98 s,v70 T5 and n/a are ALL M4.4 from the factory.
So....fuel pressure should be constantly 43.5 psi all the time.
Variations in fuel pressure are for M4.3 and LH 3.2 Jetronic which have FPR on the fuel rail.

Post by **bmdubya1198** » 09 Nov 2019, 16:38

Also, you may have the regulator on the back left corner of the engine bay, just above the steering rack. Just follow the fuel line back.
That could possibly be an issue if your fuel pressure is low.

Post by **800artfreed** » 01 Jun 2020, 19:21

Just catching up on this post. I lowered the air pressure on the injector cleaner tool to below 30 psi. Everything worked as it should. The engine ran at idle and the cleaner was passed into the injectors, not back to the fuel tank. Thanks everyone for your input.