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Discussion Starter · #1 · (Edited)
I have a problem, a difficult in engine starting.
Usually I only get good starting in the second try.
I checked the parameters of the fuel pump:
1. The pressure in idle is 43PSI, which is OK.
2. I checked the fuel flow in 10 seconds, on and off five times in a row (2 seconds each time), the volume: 200 ml, when the minimum required is about 70ml, so that is also OK.

Oddly, in Haynes book and Honda technical book, both do not mention a drop in pressure before starting ( 2sec After Switch ON). It is a problem?
I was taking a video, and that's how my "problem" looks like:

I found the Partzilla excellent video (link below):

Another excellent video[Rocky Mountain ATV MC] that explains how to test the fuel pump I found at the following link :
According to this explanation, starting at 5:20, I have a problem with the one-way valve.
In the CBR250R there is a one-way valve on the fuel line?

And there is also this great video [Ignite Moto] that explains how to disassemble and assemble our fuel pump (CBR250R):


Where is MY problem and what to do to fix it?
Thanks!!!
 

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Discussion Starter · #4 ·
An Updating
I switched to an OEM new fuel pump motor, No Change: After 2 second switch ON, there is a dramatic drop in the fuel pressure, until it reaches to zero.
I checked the parameters of the NEW fuel pump:
1. The pressure in idle is 42PSI, which is OK.
2. I checked the fuel flow in 10 seconds, on and off five times in a row (2 seconds each time), the volume: 145 ml, when the minimum required is about 70ml, so that is also OK.

Is this a problem? OR this is how it should to be ???
44808
 

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Check whether there is any voltage drop to the fuel pump. Just pinch the wire to measure live voltage. Let's see if there any Supply voltage issues or not.
 

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Discussion Starter · #6 · (Edited)
Check whether there is any voltage drop to the fuel pump. Just pinch the wire to measure live voltage. Let's see if there any Supply voltage issues or not.
I measured 12.4V. The pump receives the battery voltage(12.4V) for 2 seconds, reaches the required pressure of 43PSI. Once the engine is running it is running just fine.
The question is What should happens to the fuel pressure after those two seconds (And before pressing the start button)?

I did not find information in the technical literature, here in the forum ... On YouTube I found this: Starting at 5:20 . According to this section on YouTube, the pressure should not drop even when the pump voltage is off.

Is it normal or abnormal for the pressure to drop as described above?
 

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Now that I have seen both the videos that you have shared, to compare with your "problem" there is actually sudden drop in pressure in when ignition is ON but no drop when engine is running (As you said).
Now that we can eliminate fuel pump and filter and voltage supply. I would suggest to remove the fuel injector and check whether there is leak through it, as there should be no sudden pressure drop when Ignition is ON (unless and until there is leak).
 

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Discussion Starter · #8 · (Edited)
... I would suggest to remove the fuel injector and check whether there is leak through it, as there should be no sudden pressure drop when Ignition is ON (unless and until there is leak).
I have not found any information in Honda's technical literature. Thanks for the encouragement. You also understand that there should be no pressure drop (switch ON, engine off). I'm was not sure I'm was looking for a real problem, so the problem is real, OK. I was replacing all O-Rings in the pump structure, but did not investigate with a magnifying glass if there a crack in the plastic structure ...
Well, now as your advice, I will check the fuel injector, and we will see what I will find there. Thanks!!!

Updating
I made a tool and I will wait 24 hours for the glue to dry ...
P.S. To allow accessing to the screw it was necessary to remove the IACV as well.
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I think you want to use injector cleaner spray to check the results (without actuating the injector), nice idea.

But the simplest way is just pull (need to remove bolts) out the injector (without removing electrical connector and fuel line) turn the ignition switch ON and check.
 

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Discussion Starter · #10 · (Edited)
I think you want to use injector cleaner spray to check the results (without actuating the injector), nice idea.
I do "actuating the injector", I intend to give the injection a 9V battery voltage.

But the simplest way is just pull (need to remove bolts) out the injector (without removing electrical connector and fuel line) turn the ignition switch ON and check.
Yes, a good thought(y)(y)(y).
P.S. For that test you need to catch the injection with a zip tie.
44816

The execution got a little complicated for me. The IACV needs to be removed so that the injector screws, the on screw "up", can be accessed. So I took IACV out. When IACV was outside, I assembled everything except two connectors:
1. The fuel injector.
2. The IACV.
And like this the computer did not supply voltage to the fuel pump. At this point, when the injector was in my hands, I preferred to clean it.

Updates
So I cleaned the injector, it was not dirty, nor did it appear to be leaking.
And before final assembly I tried your offer again, this time
1. The fuel injector full Connected.
2. The IACV NOT Connected.
The experiment was successful:) (y) , the injector does not leak, BUT still, immediately after those 2 seconds a fast pressure drop begins.
See the video attached below:
 

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Discussion Starter · #12 ·
1. as long as you have pressure when engine is cranking or running, everything is OK
Thanks!
DannoXYZ a drop in pressure before starting, 2sec After Switch ON, engine OFF, It is a problem???

2. difficulty starting is most likely IAT. Follow service manual procedure to test it.
Yes, a good thought(y)(y)(y).
 

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Discussion Starter · #13 · (Edited)
...IAT. Follow service manual procedure to test it.
I do not have the "HDS pocket tester" device.

From the tests I was able to perform, these are the results:
The 5 wire (side conector) is OK (all wires lead pin to pin and are not shortened to ground or to themselves).
G/W - Y/R 4.98V OK
Y/R - Ground 2Kohm, (NOT continuןty) OK???
G/W - Lg/Y 3.5V OK???
Lg/Y - Ground 187Kohm, (NOT continuןty) OK???

No DTC fault code is recorded in the computer's memory.

But it seems that something is not quite right in the starting process, the starting is not good, when the engine is cold it takes a few seconds until it goes up to 2000RPM.
Look here:
So I consider ordering the Sensor Unit, and replacing it at the next Scheduled Maintenance.
 

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Hey @Tamir my bike rpm also goes up to 2000rpm sometimes in normal whether condition and sometimes when I park the bike for couple hours it again takes some time to settle down like cold starting (to ~1400rpm which is specified in service manual).

As you have checked the wires and there is no short circuit to ground or themselves, so connection is OK. I'm attaching the IACV diagnosis procedure in case if don't have,
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And I'm sure that will be OK, but still checking it few times can eliminate the fact that 'there might be chance that it get stuck sometimes'.

And at last I'm still confused about the sudden pressure drop result.
 

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Discussion Starter · #16 · (Edited)
And at last I'm still confused about the sudden pressure drop result.
DannoXYZ suggests that the problem is elsewhere, in IAT: Intake Air Temperature.
2. difficulty starting is mosy likely IAT.
The IAT is part of THE Sensor-Set(16060-KYJ-901) that includes 3 sensors in One Part.
1. IAT (Intake Air Temperature)
2. TP (Throttle Position)
3. MAP (Manifold Air Pressure)
my bike rpm also goes up to 2000rpm
YES' it is NORMAL
But my engine, when the engine is cold, it starts at 1250 rpm, so it almost Turned-Off, then rises very slowly to 2000RPM, until it warms up and then drops to 1400.
The first part of the process (1250RPM to 2000RPM) is incorrect.
See attached video
 

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Discussion Starter · #17 ·
Don't worry about pressure when engine is OFF. Measure pressure when you push START button. What is that pressure?
The whole idea of preliminary pressure, is to assist to starting, because the pump takes a few seconds to build up pressure. If you wait more than 2 seconds(After switch ON) and the pressure drops till zero, then all the "preliminary pressure assist" no longer assist, and the engine starting is more difficult.
There is no information about "preliminary pressure assist" in Honda Technical Book (Or in the Haynes Guide). I know that the pressure should be maintained (TO assist...), there should be a one-way valve that keeps the pressure from falling until the moment the ignition button is pressed.
See the video here.
starting at 5:20
But perhaps low-volume motorcycles like CBR250R do not have a one-way valve?
I ask because I do not know:rolleyes:???
Measure pressure when you push START button. What is that pressure?
The START button activates the pump and the pressure rises.
When my engine is running the pressure is stable and normal 43PSI
 

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Priming pump comes from back in CIS injection days with high-pressure +200psi.

With modern EFI, no priming is needed because pump can generate necessary pressure 43psi immediately when pump is activated.

Autos do not turn on pump until engine is cranking. They have no problem starting.
 

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Discussion Starter · #19 · (Edited)
Priming pump comes from back in CIS injection days with high-pressure +200psi.

With modern EFI, no priming is needed because pump can generate necessary pressure 43psi immediately when pump is activated.

Autos do not turn on pump until engine is cranking. They have no problem starting.
OK but Your claim is inconsistent with the data I measured in my CBR, and does not match the claims from the two videos I posted here at the opening thread(not my videos). The pump does not build pressure from 0 PSI to 43 PSI in two seconds, but builds some primary pressure. Otherwise why do EFI todays ("modern ") systems, and also that of Honda, give 2 seconds primary pressure?

The Answer: Because they do think it helps the starting process.

In modern motorcycles it is common for the pre-pressure to be maintained by a one-way valve. And here at CBR250R(2013) I have no idea what's going on, and I suggested that maybe because it's a small engine, Honda has given up the one-way valve (because smaller engine are easier to start). But that's my guess. I'm looking for someone who knows the answer without guessing.
 

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Yes, me too are trying say what you have said.
Priming is the first step to build sufficient pressure.

We have already know that EFI system just need one touch of start button in cold start (or any start) the bike, it's possible only because there is preparation carried out In Priming phase.

To be more specific
In cars there is return line(from different locations of fuel circuit) to release excess pressure build up in the system at various stages.
But CBR even though there is no return lines pressure drop is significant in just 2sec of primary phase, i don't know what going here.

Now that we are making circles and lots of question marks, i would suggest/request you guys to do the pressure test on another CBR250R as I don't have the tools, in this way we can clear fact about pressure drop in our bike.
 
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