• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

740 b230 line pressure regulator questions

B

bwright002

Active member
Joined
Feb 12, 2005
Hi all,
Trying to isolate a cold starting issue, and I have a question or two about the line pressure regulator at the front of the fuel rail on a b230 (Regina ignition) engine. The car runs great once it's been started and run for a minute or two. Then it's great for about the next 3 to 4 hours or so.

I'm wondering if a faulty line pressure regulator would make this engine hard to start when temperatures are below freezing? Also, what is the main purpose of having this accumulator? Is it to store fuel pressure so that the engine gets fuel immediately after turning the key, or is it to keep fuel from draining back to the tank when the car is turned off?

Also are there differences in the sizes of the regulators? I picked up a fuel rail from an identical year/engine/model car at LKQ, but the line pressure regulator's container (bowl, tank or whatever the right term is) size is about twice the size of the one that was on my car? Would swapping the line pressure regulator for the larger one likely improve my cold start ability, or make it worse?

thanks,
Bruce
 
The fuel pressure regulator assures proper fuel pressure to the injectors. Though you don't say, since it is a Regina, I'm assuming it's an 89, 90 or 91 740. The FPR for Reginas is a 2.5 bar unit. Bosch ignition units use a 3 bar FPR which would make your line pressure a bit high. More importantly, there is a TSB out for the Regina cars concerning the cold start injector. Volvo recommends rewiring the cold start injector to the starter so it only works while cranking to reduce flooding. If your car hasn't had this done AND the FPR is a 3 bar, you're probably getting too much fuel on cold starts.
 
Thanks for the clarification on what the pressure regulator's function is. The car is a 91 745.
The FPR from my car and from the parts car (also a 91 Regina 745) are different sizes though. Is the 3 bar FPR larger or smaller in overall size than the 2.5 bar version? According to my mechanic the TSB for the Cold Start Valve has been done.

So if the car won't start easily on the first try when it gets colder than freezing, is the car likely getting too much or too little fuel?

Yesterday, I was checking the LPR to see if it leaked any gas when I unplugged the vacuum hose to the intake manifold. No leaks, but I noticed that the hose was cracked where it bends. I've replaced the hose and let the car sit overnight (just around the freezing point outside). Started first time this morning, but I'm going to wait until it gets colder this week before I declare the issue resolved.

Again, thanks for the assistance.
 
The winter weather kicked in last night and we got down into the teens for temperature with added windchill factor. That new vacuum hose seems to have helped considerably. Started first time this morning (parked outside), and then again at noon (just testing).

So the lesson here seems to be, check those vacuum hoses before messing around with anything else (and given that I also have a K-Jet car too, you'd think I'd have learned that by now). Again, too soon to call this a success, but I'm thinking good thoughts here.
 
Ah the week started with such promise, but each morning this week has been below 25F, and the cold start issue is continuing to trouble me.

It will finally start, but only after a lot of cranking, letting it sit for a minute or so, and then trying again. I also hook my other brick (while running) up to the battery as I do the cranking, so I don't kill the battery in the wagon. Having the extra battery power seems to make it easier to start, as well as making sure I don't kill the wagon's battery while cranking.

Is it too much gas, or not enough gas that is the cause of the hard starting? And would a larger or a smaller FPR be better for cold start conditions?
Thanks in advance for any wisdom.
 
Try spraying some starting fluid into throtle intake?
Sounds [/B]like a "whole thing" getting started ..esp in that cold..
 
If the car only hard starts in relatively cold weather, I'd be inclined to check the engine coolant sensor. It's under the intake by cylinder #3...some folks are able to get to it w/o pulling the intake but I'm not that fortunate. Not only can the sensor go bad, the harness connector that attaches to the sensor can deteriorate/disintegrate...
I re-read your op and a comment on attempting to isolate issues such as hard starting. IMHO, these cars often have a number of sensors operating at the low end of acceptable. Individually, the sensors may test ok (but at low side of ok). Combined, the input from several low functioning sensors makes the entire engine run like crap. I'm not a big fan of throwing parts at engines...but when I do a stage zero on a new-to-me Brick I take a really good look at sensor readings; both at the sensor and at the ecu. The O2 gets replaced automatically unless I know how old it is...
 
I'm with you on the difficulty of getting to the engine coolant sensor (I've been referring to it as a "thermo-time switch" in my earlier posts, perhaps in error). I've already pulled it and replaced it with another used one (really had a fight to get it back in). Same issue as before I swapped it.

I believe that you are probably correct that the harness might also need to be replaced, and I've actually obtained one (from a picknpull) from the identical model 745. However, given the really cold weather here, I'm not very eager to try a full harness replacement outside.

I will try the starting fluid method as well, but forgive me for not knowing which hose/opening to use when spraying it in. On a b21ft, I do know which vacuum hoses to use, but not on this b230 (Regina).
 
Quick question (and a bump in the process)
If the car doesn't want to start in the cold, what is the most likely correct description of what's happening?

Is it because it has too much gas to the air available and won't easily ignite?
Is it because it has too little gas, because the cold start injector isn't sending more fuel at cold temps?
Is it because the spark being delivered isn't strong enough to light a cold engine fuel/air mixture, but can ignite the mixture once the engine starts to get warmer?

I've looked through my Bentley's and through this forum but haven't found the answer. Sorry if this is a very basic concept, but I'm just trying to better understand the underlying problem as well as finding a solution.

Thanks much.
Bruce
 
I think if it started up with the starting fluid then it woul dindicate too much air in mix.so 2 and 3 from above..
as soon as it burns off then would expect to die if mix prob.......
1 would be intake problem??vac leak??

I also second the sesnor thing swift justice was talking about..it may start but if ECu is seeing crazy it will act crazy..
 
Last edited:
swiftjustice44 said:
The fuel pressure regulator assures proper fuel pressure to the injectors. Though you don't say, since it is a Regina, I'm assuming it's an 89, 90 or 91 740. The FPR for Reginas is a 2.5 bar unit. Bosch ignition units use a 3 bar FPR which would make your line pressure a bit high. More importantly, there is a TSB out for the Regina cars concerning the cold start injector. Volvo recommends rewiring the cold start injector to the starter so it only works while cranking to reduce flooding. If your car hasn't had this done AND the FPR is a 3 bar, you're probably getting too much fuel on cold starts.
Click to expand...
Hey this is wrong. Regina runs 3 Bar according to the greenbooks. I read this years ago and went down the rabbit hole of sourcing this elusive fuel pressure regulator just to find out after installing one that we were wrong. Im sure hundreds of people have made the same mistake of trusting a forum post for factory specs over the greenbooks.

 
B307 said:
Hey this is wrong. Regina runs 3 Bar according to the greenbooks. I read this years ago and went down the rabbit hole of sourcing this elusive fuel pressure regulator just to find out after installing one that we were wrong. Im sure hundreds of people have made the same mistake of trusting a forum post for factory specs over the greenbooks.

Click to expand...
Good find! I'm curious though, I have seen a few regina 740/940s with an oddly slimmer FPR compared to the typical 3 bar units. I thought nothing of it at the time, but is there anytjing to indicate that there was a different factory spec for fuel pressure on Regina compared to LH2.4? Are there any benefits to running .5bar lower fuel pressure, ie better economy etc?
 
You must log in or register to reply here.
Back
Top