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FR691 runs great until...

#1

L

LawnWizard

FR691 with 155 hours. Starts and runs perfectly for about 15 mins then starts missing really badly. New plugs, fuel and air filter. Adding a little choke helps it smooth out but not 100%. Steering arms in and out seems to make no difference, neither does turning off PTO, so I'm thinking fuel issue (not safety switches or electrical). I'm thinking fuel pump (but unlikely) or junk in carb??? Any thoughts before I start throwing parts at it?


#2

7394

7394

Remove fuel line after the fuel filter, Turn key on & see how the flow is.

If that is fine, then carb may need a good cleaning.


#3

L

LawnWizard

Remove fuel line after the fuel filter, Turn key on & see how the flow is.

If that is fine, then carb may need a good cleaning.
I don't believe turning on the key will make a mechanical fuel pump make the fuel flow without the engine running.


#4

7394

7394

Ur right... My bad.


#5

L

LawnWizard

Ur right... My bad.
Thanks anyway! Appreciate it.


#6

B

bertsmobile1

I don't believe turning on the key will make a mechanical fuel pump make the fuel flow without the engine running.
This is why we continually beg people to supply the FULL MODEL numbers from mowers & engines because as I have never come across a FR 691 with a mechanical pump I would have given you the same answer and I have installed better than 50 of them as replacements because I used to get them cheap from RGS
So in my shop I would have first checked both the carb to manifold & the manifold to head bolts were tight
Then I would have gone to mow with a trigger pack of WD 40 or similar with me
When it started to play up I would have saturated the carb to manifold joint then the manifold to head joints , listening for a pronounced change in engine note
Next I would have plugged off the vent tube to the manifold , on some you need to remove the blower housing to do this , again a lean air leak s suspected
IF none of these made any difference then I put a 1/2 gallon of fuel is a substitute tank and hook it up to the carb high enough to gravity feed
If still no difference then I have some plugs that replace the fuel solenoid or an old one with the pin chopped off .
Still no joy then I put a pair of in line spark testers on the mower so I can visually see if there is a difference when the engine starts to run badly
Still no difference I shoot the mower .


#7

L

LawnWizard

This is why we continually beg people to supply the FULL MODEL numbers from mowers & engines because as I have never come across a FR 691 with a mechanical pump I would have given you the same answer and I have installed better than 50 of them as replacements because I used to get them cheap from RGS
So in my shop I would have first checked both the carb to manifold & the manifold to head bolts were tight
Then I would have gone to mow with a trigger pack of WD 40 or similar with me
When it started to play up I would have saturated the carb to manifold joint then the manifold to head joints , listening for a pronounced change in engine note
Next I would have plugged off the vent tube to the manifold , on some you need to remove the blower housing to do this , again a lean air leak s suspected
IF none of these made any difference then I put a 1/2 gallon of fuel is a substitute tank and hook it up to the carb high enough to gravity feed
If still no difference then I have some plugs that replace the fuel solenoid or an old one with the pin chopped off .
Still no joy then I put a pair of in line spark testers on the mower so I can visually see if there is a difference when the engine starts to run badly
Still no difference I shoot the mower .


#8

StarTech

StarTech

Nor have I; just the vacuum operated fuel pumps.


#9

StarTech

StarTech

Nor have I; just the vacuum operated fuel pumps.


#10

L

LawnWizard

Bert, thanks for the detailed method of sharing how to chase the fuel issue it seems to be having. I thought that I had been detailed enough in describing the issue. The FR691V is mounted on a Husqvarna Z254f and is NA. I was unaware that that were EFI versions of that engine out there.


#11

L

LawnWizard

This is why we continually beg people to supply the FULL MODEL numbers from mowers & engines because as I have never come across a FR 691 with a mechanical pump I would have given you the same answer and I have installed better than 50 of them as replacements because I used to get them cheap from RGS
So in my shop I would have first checked both the carb to manifold & the manifold to head bolts were tight
Then I would have gone to mow with a trigger pack of WD 40 or similar with me
When it started to play up I would have saturated the carb to manifold joint then the manifold to head joints , listening for a pronounced change in engine note
Next I would have plugged off the vent tube to the manifold , on some you need to remove the blower housing to do this , again a lean air leak s suspected
IF none of these made any difference then I put a 1/2 gallon of fuel is a substitute tank and hook it up to the carb high enough to gravity feed
If still no difference then I have some plugs that replace the fuel solenoid or an old one with the pin chopped off .
Still no joy then I put a pair of in line spark testers on the mower so I can visually see if there is a difference when the engine starts to run badly
Still no difference I shoot the mower .
I describing the fuel pump, I thought there were only 2 kinds out there. The vacuum operated one on the side of the engine cover and EFI. I guess I should have called it "vacuum" rather than "mechanical"?


#12

7394

7394

Life goes on..

The vacuum pump can be tested by unhooking the one end & crank the engine to check flow.


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