sluggish..? no acceleration...?? answer...

[Loyale93v]

well the answer to MY problem is this...I drive the 93 Loyale EA82; after a FULL tune up the car still is not performing properly. first test... fuel pressure test: spec is 21 - 25 psi controled @ idle. Max is 35 - 50psi so I set up the fuel psi tester and the psi @ idle is 21. (on the fuel in line) removed hose from bottom of fuel pressure regulator...no change ..and at WOT; no change. I discovered that there is NO vacuum comming from the little metal tube that the hose from the bottom of the fuel reg plugs into. I checked the manifold vac and it is 18(with in spec) so the symtom of lack of power is being caused by a lack of vac to the fuel reg,

SO...my question is what is causing the lack of vac from the little tube under the TB??!! I hooked a hose to it and was able to blow air through it. so it doesn't seemed clogged.

any one have any insight on this one???

[ihscout54]

I do not have a clear answer for you but I played with this once trying to solve a rough idle issue. This system doesnt work the way I assumed it would. The port for that vac. line is above the throttle plate so there will be no vaccume to the regulator at idle. I tried to get a vac. signal there and found very little, no matter what I did. So I concluded that it needed very little vaccume to function. This was a few months ago in the middle of my SPFI swap so my memory is a little fuzzy.

[Loyale93v]

I do not have a clear answer for you but I played with this once trying to solve a rough idle issue. This system doesnt work the way I assumed it would. The port for that vac. line is above the throttle plate so there will be no vaccume to the regulator at idle. I tried to get a vac. signal there and found very little, no matter what I did. So I concluded that it needed very little vaccume to function. This was a few months ago in the middle of my SPFI swap so my memory is a little fuzzy.

 

well at A.S.E. school I attend last night (my instructor worked for Subaru from 1980 - 1995) we were having trouble pin pointing the cause, however, it was suggested to me that if I were to disconnect a vac line from some where else not vital, and plug it into the bottom of the fuel reg it may help things out a bit. Of course some other function may me lost in the process, but at least the drivability concern is temporaly delt with until I can close in on the actual cause.

[ihscout54]

if I were to disconnect a vac line from some where else not vital, and plug it into the bottom of the fuel reg it may help things out a bit.

 

If you go this route you must use a ported vaccume line off the front of the throttle body. Tap into the line to the egr valve. Better yet put a vaccume gauge on it first and work the throttle, there will be some vaccume at the line to the FPR. (there just isnt much) Dont use manifold vaccume as this will make the FPR function incorrectly.

[GeneralDisorder]

As stated the vacuum is ported to the FPR - you will get nothing at idle.

 

Your spec for the fuel pressure is wrong. It is supposed to be a constant 21 psi. Your fuel pressure is dead on.

 

Look elsewhere for your problem.

 

GD

[4x4_Welder]

Sounds like a skipped timing belt, or plugged cat. Make sure the MAF is clean as well.

[Loyale93v]

Sounds like a skipped timing belt, or plugged cat. Make sure the MAF is clean as well.

 

MAF is clean, in fact it looks practically brand new. the blocked or rerstricted CAT is a good idea. It sounds like it is missing when I listen closely to the sounds from the tail pipe: "blub, blub,.........blub........blub,blub, blub"

the fuel pressure spec are from "alldata" and yes 21psi is dead on, however when throttle is applied, vac should go to the FPR and raise the FP to the spec of a min 35 and max 50 psi. the regulator is functioning only, there is no vacuum during acceleration. why not? I dunno. that my friend is the question of the day.

[ihscout54]

Your spec for the fuel pressure is wrong. It is supposed to be a constant 21 psi.

 

Not sure how I missed that, I have the FSM. I checked my fuel pressure long ago and I thought it was fine at 25-28 psi. Well, we may have just solved some of my mysteries including the intermittent rough idle problem. My fuel pressure is running right around 28-30 psi, if you goose it it drops a little. I just removed the return line and ran a hose to a gas can. Sure enough perfect 21 psi so that little return line is just too small.

[Loyale93v]

As stated the vacuum is ported to the FPR - you will get nothing at idle.

 

Your spec for the fuel pressure is wrong. It is supposed to be a constant 21 psi. Your fuel pressure is dead on.

 

Look elsewhere for your problem.

 

GD

 

the FP is only a secondary symptom. the lack of vacuum being applied to the regulator is the issue.

 

Alldata fuel pressure spec for the 93 loyale sedan 2WD F4-1781cc 1.8L SOHC : max pressure(vacuum applied) 36-50psi

controlled at idle 20-24 psi

[4x4_Welder]

Are you sure those aren't the specs for an MPFI engine? SPFI usually doesn't vary, due to the injector being above the intake instead of in the intake. An injector in the intake needs to be kept at a constant pressure above the manifold absolute pressure.

[GeneralDisorder]

The specs you have are refering to using an external vacuum source (mityvac, etc) to test the regulator operation. It is not a rising-rate regulator - the fuel pressure must be kept constant so the ECU can accurately meter the injected fuel by altering the injector duty cycle. I am pretty sure on this one although I don't have my fsm in front of me. There is an electronic version over on my SPFI conversion write up page if someone wants to check. I can't get there right now as i'm on browsing from my phone which doesn't have a pdf viewer.

 

GD

[Loyale93v]

Are you sure those aren't the specs for an MPFI engine? SPFI usually doesn't vary, due to the injector being above the intake instead of in the intake. An injector in the intake needs to be kept at a constant pressure above the manifold absolute pressure.

 

I have the print out right in front of me. it is titled: 1993 Subaru Loyale Sedan(4 door) 2WD F4-1781cc 1.8L SOHC>Powertrain Management>Fuel Delivery and AIr Induction>>Fuel Pressure>Testing and Inspection and goes on to say:

NOTE: To obtain an accurate fuel pressure reading the engine must be running. Basic fuel pump operation can be verified in a no start condition by observing gauge reading while cranking engine. Fuel pressure should be approximately 21 psi (147kPa).

RELEASE FUEL PRESSURE

 

1. Remove fuel pump fuse

2. start engine and run it until it stalls

3. after engine stalls,crank it for five (5) more seconds

4. turn key to "OFF"

5. reinstall fuel pump fuse

 

CHECK FUEL PRESSURE

 

1. Disconnect fuel filter outlet hose

2. Connect a fuel pressure guage between fuel filter outlet and hose.

3. Start engine and idle.

4. Disconnect vacuum hose from pressure regulator

5. MOMENTARILY pinch return hose close and observe gauge reading (this checksfuel pump max. output pressure). If not within specification, check all delivery linesand if not pinched or restricted, replaced fuel pump. MAXIMUM FUEL PUMP PRESSURE Approx. 36-50 psi (245-343 kPa)

6. Check engine vacuum reading at pressure reulator source hose. If not within specification, inspect for vacuum leak and/or clogged fitting at manifold. ENGINEVACUUM AT IDLE More than -19.69 inHg (-66.7 kPa)

7. Reconnect hose and observe guage reading at idle. CONTROLLED FUEL PRESSURE AT IDLE 20 - 24 psi (137-167 kPa)

8. Disconnect pressure regulator vacuum hose. Fuel pressure should raise.

9. Apply more than -20.5 inHg vacuum to pressureregulator. Fuel pressure should be lower than observed in step 7.

10. If pressure reading was incorrect or didnot vary and all previous tests were OK, replace pressure regulator.

 

And that folks is what I went by when checking out the FP spec. I know...I know it does not clarify between MPFI and SPFI in writing. However, if I could scan the photos that came along with it you would see a picture of a TBI with one injector. (single point fuel injection)

Edited June 19, 2009 by Loyale93v

[Loyale93v]

The specs you have are refering to using an external vacuum source (mityvac, etc) to test the regulator operation. It is not a rising-rate regulator - the fuel pressure must be kept constant so the ECU can accurately meter the injected fuel by altering the injector duty cycle. I am pretty sure on this one although I don't have my fsm in front of me. There is an electronic version over on my SPFI conversion write up page if someone wants to check. I can't get there right now as i'm on browsing from my phone which doesn't have a pdf viewer.

 

GD

 

yes, it does use an external vac to verify manifold vac. but i am not sure what you are getting at. Please elaborate.

[ihscout54]

What he's saying is that you have the same misconseption of how this system works as I did. It was because of "motors.alldata" it got me too. It doesnt use manifold vaccume at idle to set idle pressure and then at WOT when there is no vac. it opens up to max. (This is not how this FPR works) This device is designed to keep the system at a stable 21 psi. at all times. THERE SHOULD BE NO VACUUME from that line at idle, only under heavy acceleration which may be difficult to simulate in the shop. Hence why you are not getting a vac. signal there. Your fuel pressure is right on.

[GeneralDisorder]

Having looked at the FSM, I see where the confusion lies.

 

The FPR is designed to keep a constant 21 psi of effective pressure. It lowers the fuel pressure as the throttle body vacuum increases in order to keep the pressure at the injector nozzle a constant 21 psi higher than throttle body pressure (this keeps the engine from "sucking" extra fuel out of the injector nozzle - in other words the injector squirts a known quantity of fuel when it is opened for a known quantity of time under all conditions).

 

I'm not sure what the max throttle body vacuum is as I've never tested it, but the alldata info you posted sugested 20.5 inHg. That's around 10 psi but that would mean a one-to-one ratio on the fuel pressure vs. throttle body vacuum which we have no specs on. Thus I can only say that it *might* trim the fuel pressure by as much as 10 psi (so about 11 psi on a gauge) immediately upon cracking the throttle plate open. It would probably never be that much in practice though. And it should NEVER be higher than 21 under ANY circumstances.

 

Here's the problem - ported vacuum increases to manifold vacuum as soon as the throttle plate uncovers the port then drops with the manifold vacuum and continues to drop till it's very weak at WOT. So at WOT you would expect it to be the same 21 psi that it is at idle or close to it. Thus even if the port were blocked it would only momentarily effect the fuel sytem and it would be rich, not lean. You would be unlikely to even notice this slightly rich condition and your power would be perfectly normal at WOT.

 

I surmise the reason you aren't seeing vacuum at the FPR's port is because you aren't cracking the throttle when you are testing it. It is my educated opinion that your fuel pressure is dead on and your issue lies entirely elsewhere. (I have also never seen one of these fail, so empirical evidence sugests it is highly unlikely).

 

GD

Edited June 19, 2009 by GeneralDisorder

[Loyale93v]

I surmise the reason you aren't seeing vacuum at the FPR's port is because you aren't cracking the throttle when you are testing it. It is my educated opinion that your fuel pressure is dead on and your issue lies entirely elsewhere. (I have also never seen one of these fail, so empirical evidence sugests it is highly unlikely).

 

GD

 

yes, I agree. The fuel pressure is right on. BUT, what of the vac at the FPR's port? I did crack the throttle(from under the hood). So the issue is the vacuum at the fpr's source hose. engine vac @ idle from that port should be more than -19.69 inHg. (step #6 in my earlier post) although i thought i read also from an earlier post that there is no vac from that port at idle. So who is right? at any rate ...let's suppose that there is supossed to be -19.69 inHg of vac from the fpr port, the fact that ther isn't says that there is a vac leak or clogged port or what else? what else could cause this? would a clogged CAT cause a manifold vac issue? I would think yes, but I am not sure. I test Vacuum at other ports and got a strong -18 +. There is a very deffinate lack of acceration/bogging out/ little, no or slow response from the accerator pedal while driving.

[naru]

Your "step 6" is plain wrong for a SPFI throttle body type injection system.Correct for MPFI.

 

Your FPR is connected to throttle bore vacuum,not manifold vacuum.

As the "port" is located rather high above the throttle plate,it will only see vacuum at high airflow, open throttle.Tee in your gauge and go for a drive to get a reading.

[GeneralDisorder]

yes, I agree. The fuel pressure is right on. BUT, what of the vac at the FPR's port? I did crack the throttle(from under the hood).

 

How far did you open the throttle - did you do this with the vacuum gauge hooked up?

 

So the issue is the vacuum at the fpr's source hose. engine vac @ idle from that port should be more than -19.69 inHg. (step #6 in my earlier post) although i thought i read also from an earlier post that there is no vac from that port at idle. So who is right?

 

There should be no vacuum from that port at idle. I'll even take a picture of one for you:

 

The port at the top is the FPR port - as you can see it is WAY above the throttle plate and as such receives a much reduced vacuum signal till the throttle plate is open quite far. That would be known as "Late Ported Vacuum". Your alldata is completely, 100% wrong with step #6. That's the problem with blindly following information sources like alldata - you are always going to be better off knowing the principle of operation of the sub-system you are testing than going by a 3rd or 4th party book. Sometimes even the FSM's are wrong.

 

 

at any rate ...let's suppose that there is supossed to be -19.69 inHg of vac from the fpr port, the fact that ther isn't says that there is a vac leak or clogged port or what else? what else could cause this? would a clogged CAT cause a manifold vac issue? I would think yes, but I am not sure.

 

Lets not suppose anything. Lets be SURE. If you suspect the cat then cut it open and look. It would not cause an issue with engine vacuum at idle. It might cause issues under load but that wouldn't be an issue so much as a symptom and testing engine vacuum is not the way I would go about diagnosing a clogged cat.

 

I test Vacuum at other ports and got a strong -18 +.

 

Of course you do - they aren't ported.

 

There is a very deffinate lack of acceration/bogging out/ little, no or slow response from the accerator pedal while driving.

 

That could be a lot of things. Have you checked for smooth operation of the throttle posistion sensor? Have you ran a D-Check on it?

 

GD

[GeneralDisorder]

Just so everyone is completely clear on this

 

93 Loyale's did not come with MPFI, so Alldata could only be talking about the SPFI system with respect to the vehicle they claim this information applies to. It is plain wrong and there's no way around it.

 

For that matter - step 8 is also wrong as disconnecting a port that isn't doing anything will do.... nothing!

 

GD

Edited June 20, 2009 by GeneralDisorder

[Loyale93v]

Your "step 6" is plain wrong for a SPFI throttle body type injection system.Correct for MPFI.

 

Your FPR is connected to throttle bore vacuum,not manifold vacuum.

As the "port" is located rather high above the throttle plate,it will only see vacuum at high airflow, open throttle.Tee in your gauge and go for a drive to get a reading.

 

interesting. throttle bore vacuum. mmmmmmmmm. how did I miss that. it does say check for clog or leaking fitting at manifold doesn't it. Well, back to the drawing board.....

 

some one had installed an after market CAT on the exhaust system. I never hear good things about after market CAT's it could be restricted. I do hear a "blub, blub......blub.....blub,blub,blub" from the tail pipe. Miss fire? restricted cat?

[GeneralDisorder]

Sounds like a classic misfire to me. Have you tested the coil?

 

Seriously - run a D-Check and see what you find.

 

GD

[Loyale93v]

Sounds like a classic misfire to me. Have you tested the coil?

 

Seriously - run a D-Check and see what you find.

 

GD

 

i have not tested the coil as of yet. only I have replaced coil to cap wire, rotor, cap, plug wires and spark plugs.

 

D-check using a DVOM? do you know the FSM spec's ?

[GeneralDisorder]

No - The D-Check is a special self-diagnostic mode built into your ECU.

 

Read the SPFI section of the FSM here on my conversion write up page:

 

http://home.comcast.net/~trilinear/EA81_SPFI_doc.html#final_thoughts

 

It's the very last link on the page - the 1989 engine section PDF.

 

But if you learn how to use your DMM (DVOM, whatever - most are not strictly DVOM's these days), you can test out most of the system to insure it's proper operation without ever turning on the car..... The D-Check is very useful for intermittent problems that only show up while driving, etc.

 

GD

[Loyale93v]

No - The D-Check is a special self-diagnostic mode built into your ECU.

 

Read the SPFI section of the FSM here on my conversion write up page:

 

http://home.comcast.net/~trilinear/EA81_SPFI_doc.html#final_thoughts

 

It's the very last link on the page - the 1989 engine section PDF.

 

But if you learn how to use your DMM (DVOM, whatever - most are not strictly DVOM's these days), you can test out most of the system to insure it's proper operation without ever turning on the car..... The D-Check is very useful for intermittent problems that only show up while driving, etc.

 

GD

I went to the suggested site but for some reason my computer does not want to cooperate with me today! I can't seem to be able to read the pdf file! I have ADOBE READER. I don't get what is going on with it!? computers is definately not my thing. I know this much about the D-CHECK...I connect the two green connecters under the hood and having previously removed the panel under the steering column, turn the key to the run position with out cranking the engine. The little red light flashes seven (7) times then a pause then flashes seven (7) more times, and just does that pattern continuosly. then I unplugged the green connecters and plugged in the small white-ish ones. The chech engine light on the dash flashes on and off continuosly. i think the ecu light is also flashing aswell. so what do we make of this ?does it mean anything? Is there something more that I can do to run the "D-check"?

[4x4_Welder]

Just so everyone is completely clear on this

 

93 Loyale's did not come with MPFI, so Alldata could only be talking about the SPFI system with respect to the vehicle they claim this information applies to. It is plain wrong and there's no way around it.

 

 

GD

 

And just so we're completely clear on this- What makes you think their procedures cover only the SPFI Loyale and they didn't just throw in the info for the MPFI Legacy? I have never liked aftermarket repair resources, I always go with a site like this or an FSM if one is available. Very rarely have I seen a third-party manual that had in depth info. Usually they basically take 500pages to say if you need this book, take it to a shop.