Cylinder #1 Pressure Sensor

FordGolfer7 · Jul 16, 2018

Can anyone explain to me (novice in the diesel field) what the pressure sensor installed on #1 injector does? What it's purpose is? How it affects the running of the engine? Should there be any wires attached to it? Anything that will help me understand this device will be greatly appreciated.
I have an 89 F350 with the 7.3 IDI, changed the injector pump and injectors, having hell getting it to run properly.

Black dawg · Jul 16, 2018

It does nothing for the engine. It is a piezo sensor, that can produce a pulse signal for some timing meters.

Agnem · Jul 16, 2018

Don't try to delete it. If you really want to do that, get yourself a new #1 injection line from a Van. Deleting it would shorten the line and mess up your timing.

nelstomlinson · Jul 16, 2018

I was just going to ask what the little can on the injector line immediately above the injector on my '89 crew cab was all about. It sounds as if it's a pressure sensor? Funny that none of my other IDIs have one. Was that on all of the IDIs originally, or just on some? Also, what do we hook up to it to use it?

IDIBRONCO · Jul 16, 2018

The 7.3's all used them. The 6.9's did not except maybe for the 1987 model that looks like a 7.3. I can't remember on that one.

icanfixall · Jul 16, 2018

That is NOT a pressure sensor.It is the brass connector the Rotunda timing meters clamp on. Thos meters no longer are used. Most here use the kent moore j33300-a meters. they connect to the hard line on one or four injector line and one mag sensor to the crank. Thats it.As Mel suggested. to replace it you need the number one hard line for the van engine applications. they time off the number four cylinder because its easier to reach. Vans are tight up front to see anything.

FordGolfer7 · Jul 17, 2018

Thanks very much for the information, I have asked a lot of people in my local area and did not get an answer. I have purchased a Rotunda Timing Meter and hope it works well.

IDIoit · Jul 17, 2018

i do away with the 7.3 lines, and use 6.9 lines.
i dont like the look of the adapter.
i also time mine with a kent moore

icanfixall · Jul 18, 2018

All 7.3 injectors are raised out of the precups 60 thousands for better emissions compliance so... The injector lines are that much shorter. A so again using 6.9 hard lines on a 7.3 is not a perfect fit..But most c make them fit. 60 thousands is not much.san

chris142 · Jul 18, 2018

Why would a shorter line effect the timing? If that line is 2 inches long or 2 miles as long as its full of a non compressible liquid a 1/4 inch movement on one end will cause a 1/4 inch movement on the other end

DrCharles · Jul 19, 2018

Because it takes a finite time for the pressure wave to travel through the line, and the engine is rotating during that time

I haven't done the math but I think even 1/4" of line length would be a fraction of a degree at max rpm. Anyone got real numbers?

franklin2 · Jul 19, 2018

chris142 said:
Why would a shorter line effect the timing? If that line is 2 inches long or 2 miles as long as its full of a non compressible liquid a 1/4 inch movement on one end will cause a 1/4 inch movement on the other end

I have seen this said over and over many different places, so I will agree it must affect it somehow. But I was in a pinch away from home a few years ago, my #1 line cracked while I was on vacation. The only line I could find was one off a 6.9 in the junkyard. I used that line, and the truck seemed to run fine, and I am still using that line on it. I can't tell any difference.

Thewespaul · Jul 19, 2018

It won’t make much of a difference if your injectors arent pressure matched in the first place

nelstomlinson · Jul 19, 2018

chris142 said:
Why would a shorter line effect the timing? If that line is 2 inches long or 2 miles as long as its full of a non compressible liquid a 1/4 inch movement on one end will cause a 1/4 inch movement on the other end

What's the speed of sound in diesel? That's how fast the pressure wave propagates.

DrCharles · Jul 19, 2018

Well if I knew that, I'd have posted it

OK, I'll do just a little more of the exercise "Calculation left for the student". Speed of sound in diesel is 1250 meters per second, or 1.25 meters per millisecond, or 49.14 inches per millisecond. Oh what the heck, I'll walk through it

Now figure out at a nice 3300 rpm that is 0.0182 second per 360 degree revolution. 18 msec to cover 360 degrees --> 20 crank degrees in 1 millisecond.

So a difference in line length of 4.9 inches results in a 2 degree difference in timing. Or just about two and a half inches per degree. Therefore the approximately 3/4-inch length of the pressure sensor will make a difference of 0.3 degrees on that one cylinder, and that's at maximum governed RPM. Obviously at lower revs the difference will be proportionally less.

I think that it'd be lost in the noise from differing injector pop pressures, myself.

Cylinder #1 Pressure Sensor

FordGolfer7

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Black dawg

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Agnem

Using the Force!

nelstomlinson

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IDIBRONCO

IDIBRONCO

icanfixall

Official GMM hand model

FordGolfer7

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IDIoit

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icanfixall

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chris142

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DrCharles

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franklin2

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Thewespaul

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nelstomlinson

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DrCharles

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