My 89 Volvo 740 Turbo Intercooler that I have had for just over one year has always been a slow starter. A mechanic told me that it needed a new fuel regulator a while ago. I want to do the repair myself and I want to make sure that this is what it is.

The car had a new fuel pump installed before I got the car. I saw the receipt and also talked to the mechanic to confirm that this was done. So I am pretty confident that the fuel pump is not the problem.

When I start the car after it has been sitting for a few days, it fires up right away on the first try. If I have driven the car the day before, it starts slow in the morning usually. Also if I am driving the car and then park it and then restart it, it cranks for a few three to five seconds before starting up (slow start).

Can anyone tell me if this is surely a fuel regulator issue like the shop owner told me? Is there a test that I can do (i am not getting any codes on the dash).

Thanks for any input.

 

to test the fuel pressure regulator, you need a fuel pressure gauge, with the right adapters to hook it inline between the incoming fuel line and fuel rail.. it should be 40-44 PSI above manifold vacuum.

note there are two fuel pumps, one in the gas tank, and one under the car. tha tank pump 'delivers' fuel under low pressure to the main pump, the main pump creates said 40+ PSI, sends the fuel to the fuel rail, then the fuel pressure regulator 'bleeds' off excess pressure, and sends the fuel back to the tank. the fuel pressure regulator has a vacuum hose to the intake manifold, so under low or negative (boost) vacuum, there's higher absolute fuel pressure.

I would *think* low fuel pressure would cause lean burn conditions, and possible fuel starvation at high throttle/rpm combinations.

 

The check valve on the fuel pump went bad on my car. Every time I'd start the car after just having driven it a within a few hours it would take a lot more cranking. It maintains fuel pressure in the high pressure side of the system when the cars sits for a while. That's cheap and easy to do (I replaced the little fuel line that connected directly to it too). It will be a apparent if you can test the fuel pressure and shut the car down and see that it maintains that pressure. Of course this does not explain what after a day of sitting it will have a long time of cranking for the engine to catch. maybe it does hold pressure for a few days. Oh yea, after I replaced mine, the car catches very quickly when warm.

 

when you turn the key on, the fuel pump runs for a second, that check valve just has to hold the pressure until the engine turns over and the pumps come on again.

 

That's what I thought, but my 89 740 Turbo does not start the pumps until the hall sensor detects engine movement. It may be an LH2.4 thing, or a problem in my car.

 

my 92 740T (lh2.4) runs them for a second. so does our 87 240 (lh2.2 non-turbo). they are really quiet, you just about have to be under the car or with your ear to the gas filler pipe to hear them start/stop.

 

I would not doubt that there is something the matter with that part of my FI system.

 

I'd definitely change the FPR.

 

I wouldn't change the FPR unless its failing a fuel pressure test, or leaking fuel into the vacuum line (a common failure mode).

 

Interesting...

I was under the car today looking around and I think I spotted the second fuel pump (out of tank). It is not even close to new. Thanks for the information.

I plan on running the pressure tests and getting to the bottom of the slow start issue in the near future. One thing to note is that when I was looking at the fuel regulator, I noticed that the fuel lines around it were bent over. I straitened them out the best that I could and it may be a coincidence but it has been starting a little bit faster. This may have something to do with it. I'm going to try and get the kinks out the best that I can.

So not to put this project on the back burner but while I was under the car I found there were a few more projects coming my way. I will start another thread for that. At this point Im up against some minor rust and a clicking noise as well as a squeaking noise coming from my brakes.

Anyway thanks for the information and pointing me in the right direction with this.

 

the pressureregulator should be directly connected to the fuel rail, and has the fuel return line connected to it, also a vacuum line.