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Wildthings
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Joined: March 13, 2005
Posts: 50352
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 Posted: Fri Aug 11, 2017 9:31 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| Gauche1968 wrote: |
| djkeev wrote: |
To me, the injectors are being told to spray when there is no need to do so creating a flooded condition.
Let it run, pull an injector plug and check for voltage. Just pull one, they all fire at the same time. The engine will misfire without the injector working. Have someone turn off the engine while you are watching the voltage. What happens?
Does the voltage linger?
Have them turn the key on, are the injectors powered even before the key person operates the Starter?
If so, this is your flooding.
There should not be an injector pulse until the engine rotates. Your Hall Sender controls this.
If you have injector voltage, the Hall sender or the wiring for it is screwy or the ECU is messed up.
Grabbing at straws here, you've got an odd one.
Dave |
Thanks for those suggestions. Will try. There should be zero volts at the injector plugs when the engine is not running or spinning? |
With the ignition on you will see voltage on both sides of the injectors when the engine isn't running. The ECU grounds the one side of the injectors to make them fire. |
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djkeev
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djkeev
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djkeev
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| Posted: Sat Aug 12, 2017 8:44 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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Just to verify, the 24550 test light does indeed work for seeing the injector pulse!
....... affirmative, yes, go spend $15 and pick one up.
I'll post photos but I used a piece of wire in one of the injector plug terminals and the tester point in the other. Hooked the tester ground clip to the wire and Viola'! A flashing tester!
And yes, as expected, the engine idled horribly with one injector unplugged!
A length of wire, stripped on both ends and my tester.
One end of the wire is twisted and inserted into one of the injector plugs, the probe end of the tester is inserted into the other terminal.....
I carefully routed the wire so the bare clip grasping the wire doesn't accidentally ground out, if in doubt, wrap it in electrical tape.....
The entire assembly ready for use......
Dave
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Gauche1968
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Joined: April 13, 2006
Posts: 1518
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| Posted: Sat Aug 12, 2017 10:40 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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| djkeev wrote: |
Just to verify, the 24550 test light does indeed work for seeing the injector pulse!
....... affirmative, yes, go spend $15 and pick one up.
I'll post photos but I used a piece of wire in one of the injector plug terminals and the tester point in the other. Hooked the tester ground clip to the wire and Viola'! A flashing tester!
And yes, as expected, the engine idled horribly with one injector unplugged!
A length of wire, stripped on both ends and my tester.
One end of the wire is twisted and inserted into one of the injector plugs, the probe end of the tester is inserted into the other terminal.....
I carefully routed the wire so the bare clip grasping the wire doesn't accidentally ground out, if in doubt, wrap it in electrical tape.....
The entire assembly ready for use......
Dave |
Thanks Dave,
Yeah, I am going to need see some pics to put that procedure together.
I do have a new finding: The fuel pressure is now dropping when the engine with increased RPMs. That is not normal right?
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djkeev
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Gauche1968
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| Posted: Sun Aug 13, 2017 9:55 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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Probably should have mentioned it, but grounds have all been gone through. I am still curious about possible failure modes of the FPR. Should pressure increase or decrease as the engine is reved?
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djkeev
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Wildthings
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Joined: March 13, 2005
Posts: 50352
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| Posted: Sun Aug 13, 2017 11:06 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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| Gauche1968 wrote: |
Probably should have mentioned it, but grounds have all been gone through. I am still curious about possible failure modes of the FPR. Should pressure increase or decrease as the engine is reved? |
If the pressure drops as you use more fuel, it is probably a supply problem. Some kind of blockage or the fuel pump isn't up to snuff. |
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djkeev
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vwjetboat
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Joined: May 11, 2017
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Location: Florida
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| Posted: Sun Aug 13, 2017 11:33 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
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Wildthings
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| Posted: Sun Aug 13, 2017 11:41 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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| vwjetboat wrote: |
| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
??? |
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vwjetboat
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| Posted: Sun Aug 13, 2017 11:45 am Post subject: Re: Hot Start Problem After Injectors Serviced |
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| Wildthings wrote: |
| vwjetboat wrote: |
| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
??? |
FUEL PRESSURE REGULATOR its vacuum operated on the digijet system ?? what are you missing ? |
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Wildthings
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| Posted: Sun Aug 13, 2017 12:03 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| vwjetboat wrote: |
| Wildthings wrote: |
| vwjetboat wrote: |
| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
??? |
FUEL PRESSURE REGULATOR its vacuum operated on the digijet system ?? what are you missing ? |
So when the there is no vacuum most of the fuel goes to the injector? Not at idle, not at part throttle, not at full throttle, and certainly not when the injectors are turned off on decel. Under no normal operating conditions does this happen:
| Quote: |
| with no vacuum it diverts most of the FP to the injectors |
. |
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vwjetboat
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Joined: May 11, 2017
Posts: 1732
Location: Florida
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| Posted: Sun Aug 13, 2017 12:09 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| Wildthings wrote: |
| vwjetboat wrote: |
| Wildthings wrote: |
| vwjetboat wrote: |
| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
??? |
FUEL PRESSURE REGULATOR its vacuum operated on the digijet system ?? what are you missing ? |
So when the there is no vacuum most of the fuel goes to the injector? Not at idle, not at part throttle, not at full throttle, and certainly not when the injectors are turned off on decel. Under no normal operating conditions does this happen:
think about it.. at idle you need almost no fuel.. that is why it is DIVERTED to the return line so there is not a massive amount of pressure.. as you increase the throttle.. the vacuum decreases and more fuel is diverted to the injectors.. its a gradual thing.. not an off on thing.. but when the engine is off.. if the FPR has a hole in the diaphragm it will still run.. still idle and will work at cruising speed but sitting not running the fuel pressure will bleed threw to injectors when sitting.. its supper easy to change.
| Quote: |
| with no vacuum it diverts most of the FP to the injectors |
. |
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vwjetboat
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Posts: 1732
Location: Florida
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| Posted: Sun Aug 13, 2017 12:10 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| vwjetboat wrote: |
| Wildthings wrote: |
| vwjetboat wrote: |
| Wildthings wrote: |
| vwjetboat wrote: |
| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
??? |
FUEL PRESSURE REGULATOR its vacuum operated on the digijet system ?? what are you missing ? |
So when the there is no vacuum most of the fuel goes to the injector? Not at idle, not at part throttle, not at full throttle, and certainly not when the injectors are turned off on decel. Under no normal operating conditions does this happen:
think about it.. at idle you need almost no fuel.. that is why it is DIVERTED to the return line so there is not a massive amount of pressure.. as you increase the throttle.. the vacuum decreases and more fuel is diverted to the injectors.. its a gradual thing.. not an off on thing.. but when the engine is off.. if the FPR has a hole in the diaphragm it will still run.. still idle and will work at cruising speed but sitting not running the fuel pressure will bleed threw to injectors when sitting.. its supper easy to change.
| Quote: |
| with no vacuum it diverts most of the FP to the injectors |
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think about it.. at idle you need almost no fuel.. that is why it is DIVERTED to the return line so there is not a massive amount of pressure.. as you increase the throttle.. the vacuum decreases and more fuel is diverted to the injectors.. its a gradual thing.. not an off on thing.. but when the engine is off.. if the FPR has a hole in the diaphragm it will still run.. still idle and will work at cruising speed but sitting not running the fuel pressure will bleed threw to injectors when sitting.. its supper easy to change. |
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tjet 
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Joined: June 10, 2014
Posts: 3533
Location: CA & NM
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| Posted: Sun Aug 13, 2017 12:16 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| Gauche1968 wrote: |
| tjet wrote: |
How old is your fuel pump?
I'm gonna say that's the issue. |
Brand new, super deluxe Pierburg pump. |
How was it running before you replaced the fuel pump?
Also, I noticed that you stated you have a brand new alternator to starter wire.
How many things did you replace (& do - cleaned grounds, etc) at the same time you had it down waiting for the injectors to come back? |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50352
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| Posted: Sun Aug 13, 2017 2:59 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| vwjetboat wrote: |
| vwjetboat wrote: |
| Wildthings wrote: |
| vwjetboat wrote: |
| Wildthings wrote: |
| vwjetboat wrote: |
| the FPR with vacuum lets the fuel bypas to the return line .. with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
??? |
FUEL PRESSURE REGULATOR its vacuum operated on the digijet system ?? what are you missing ? |
So when the there is no vacuum most of the fuel goes to the injector? Not at idle, not at part throttle, not at full throttle, and certainly not when the injectors are turned off on decel. Under no normal operating conditions does this happen:
think about it.. at idle you need almost no fuel.. that is why it is DIVERTED to the return line so there is not a massive amount of pressure.. as you increase the throttle.. the vacuum decreases and more fuel is diverted to the injectors.. its a gradual thing.. not an off on thing.. but when the engine is off.. if the FPR has a hole in the diaphragm it will still run.. still idle and will work at cruising speed but sitting not running the fuel pressure will bleed threw to injectors when sitting.. its supper easy to change.
| Quote: |
| with no vacuum it diverts most of the FP to the injectors |
. |
|
think about it.. at idle you need almost no fuel.. that is why it is DIVERTED to the return line so there is not a massive amount of pressure.. as you increase the throttle.. the vacuum decreases and more fuel is diverted to the injectors.. its a gradual thing.. not an off on thing.. but when the engine is off.. if the FPR has a hole in the diaphragm it will still run.. still idle and will work at cruising speed but sitting not running the fuel pressure will bleed threw to injectors when sitting.. its supper easy to change. |
The fuel pump puts out enough volume so that significant fuel is returning to the tank at all times including at full throttle and high revs.
When the ECU is in closed loop the engine gets no additional fuel no matter what the manifold vacuum is as the ECU (with input from the O2 sensor) keeps the mixture at stoch.
The FPR dumps an almost identical volume of fuel to the tank during close loop operation (and almost the same at idle, and only a 15%+/- different at full throttle) at 32 psi as it does at 28 psi.
If the diaphragm is holed then the spring inside the FPR will still function just as it would with zero vacuum thus blocking any fuel from returning to the tank after shutdown.
If the diaphragm is holed the fuel pressure will drop to zero quickly after shut down and there will be zero pressure against the injectors, if the injectors will not leak through at 28-32 psi they are certainly not going to leak through at 0 psi.
If the diaphragm is holed gas is going to be leaking through the hole, into the vacuum line into the intake whenever there is pressure to cause it to, thus flooding the engine and causing it to run very poorly and stall.
Sadly, there isn't much correct in what you wrote here:
| Quote: |
| with no vacuum it diverts most of the FP to the injectors.. so when they go bad... the fuel will dump in the engine when off.. |
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vwjetboat
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| Posted: Sun Aug 13, 2017 3:05 pm Post subject: Re: Hot Start Problem After Injectors Serviced |
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| so.. fix it then.. |
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djkeev
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