EA82 SPFI Fuel Pressure Regulator

[asavage]

Well, I'm on my way to being stumped.

 

After reading more about how the fuel pressure regulator is supposed to work on my '93 Loyale, I decided to retest it.

 

Test gauge teed after the fuel filter.

 

Key on engine off, while the pump runs: 27 PSI.

After pump shuts off: 23 PSI (OK)

Cold idle = 28 PSI (spec is 20-24) (bad)

 

So, there's a problem. There is a possibility that my test gauge is miscalibrated, though. So I follow the test sequence and pull the vacuum line off the regulator and hook a vacuum gauge to it.

 

Spec is about 19" Hg. I get nada with engine iding. I used compressed air on the TBI fitting, still no vacuum.

 

Took the top off the TBI, and I can't for the life of me see how you could ever achieve vacuum at idle: the tap is bored to a single hole above the throttle plate. I did a vacuum check with a hand pump, while covering the hole with my finger, and it holds, so I'm assuming that either there is no other passage drilled down to the manifold, or that there is, but it's been plugged or occluded by some other repair. I don't want to pull it off the manifold, because it looks like I'll have to drain the cooling system, and I can't get into that tonight.

 

I'm mystified.

Both AllData and Mitchell are explicit: the fuel pressure regulator is connected to manifold vacuum. Mine isn't.

 

Help!

Somebody with a SPFI EA82 please pull the vac line off the fuel pressure regulator and verify that, at idle, there is vacuum on that port. If verified, I'll have to tear the TB off the manifold tomorrow and see what the hell is going on under there.

 

The fuel pressure regulator on a SPFI EA82 is horizontally screwed to the driver's side of the throttle body, is black in colour, has one fuel line connected to its top, and one vacuum line off the bottom (which is hard to see). On my rig, that vacuum line is about 2.5" long and is connected to a vacuum tap on the rear of the throttle body -- the port which has no vacuum at idle on my engine.

 

Even aside from this issue, I'm not getting proper regulation from my regulator: with no vacuum on it, I should see somewhere above 30 PSI (simulating WOT). I've applied 20" vacuum to the unit, and it seems to drop too low (15 PSI). Unfortunately, this is another $160 part, so 1st things 1st, I'm going to sort out this vacuum feed problem.

[mnorton]

After reading your post I decided to put a vacuum gauge on my intake port (the one that the two inch rubber hose plugs into from the FPR) and I have 0 vacuum throughout the RPM range. I sprayed brake cleaner in there and the engine started to die which tells me that the fluid was making it all the way through.

 

Does anybody know what the vacuum range should be for the port that the FPR plugs into?

 

Thanks,

Matt

[Erik R]

Mine is the same way; no vacuum to that port at idle.

I have been looking into this myself because I have a part-throttle surge problem.................but runs fine at WOT.....

I assumed the vacuum chamber was working against a spring loaded diaphram and it would make sense to have high pressure at idle, or the engine would stumble badly if you cracked the throttle open suddenly..............also would need full pressure at (or to achieve) WOT rpm's for full fuel volume.

I just want to know what pressure and volume should be present at part throttle or "cruise" rpm/load?

[mnorton]

Thanks for the reply. I tried hooking full manifold vacuum to the regulator and at iddle the car nearly died - not enough fuel I guess! As I reved it up it seemed to work well. I did not drive the car like this.

 

I may try and find another vacuum port that is nearly zero at idle yet builds vacuum with additional RPM and see what that does. I'm doing this because I have a terrible pinging/knocking problem that I cannot figure out. Maybe you have some suggestions for me. Here's the skinny:

 

1. Only pings when the outside temperature is above 32 degrees (0 here in Canada).

 

2. Will do it when I come off a right hand ramp carrying good corner speed. Once the car is level, I will take my foot off the gas and then back on and pinging stops.

 

3. Higher octance and reduced timing helps a little but not enough. Some times it will ping even when I'm going down hill

 

4. Car runs a bit rough at idle. Sounds like small "backfires" if you put your ear to the muffler. New electronics did not help at all (plugs, wires, cap, button).

 

5. Car will sometimes erratically idle from 1000 to 1250 when coming off of fast idle during the warm up process. Eventually settles down to 900 or so.

 

All of the basics have been covered except that I have not checked all the components in the fuel system.

 

Thanks for any advice you can give.

Matt

[MilesFox]

the pressure regulator is after the injector, i do believe. so its that way on mpfi.

it just sends back what the injector doesnt use up

[Erik R]

Haynes manual states that the FPR acts as a "downstream" check valve when the engine is shut down........holding the fuel pressure. Also, early models are calibrated for 14 psi idle, later ones 21 psi.

I have disconnected my fuel ines a couple of times now, and have never had ANY residual fuel pressure; just small amount of fuel........makes me wonder if mine is bad.......:cornfuzz:

[MilesFox]

well, if its not hoolding back pressure, all the fuel is going back to the tank rather than thru the injector