Barometric pressure sensor (EFI help please)

[Viperwolf1]

MAP sensors were used on Fords as far back as 1978 with the introduction of EEC1.

 

[DirtDonk]

I know that question was not directed at me, but I thought I'd throw in my earliest experience with an "electronically controlled" Ford truck.
Interestingly enough, it was an '83 F150 4wd 302 with Federal specifications.

This particular setup was using that semi-electronic carburetor and fixed non-TFI distributor. Carb looked for all the world like a 2100 series with a TPS slapped on to the side and a funky little mixture valve/motor stuck into the back side.
Distributor had a sort of a "fork" cast into it's base and the engine block had a little nub cast into it where they would line up and not allow the distributor to rotate for any timing adjustment whatsoever. Had a very interesting internal make up too. Never seen it before.

The ECM was under the seat, buried in the carpet.

Basically looked like a standard pre-EFI 302 with a few extra wires, solenoids, valves associated with the EGR, and fewer vacuum hoses running around.
Ran like crap too.
Turned out the mixture control valve in the back of the carb had deteriorated and fallen into pieces, blocking some passages and leaving others wide open. Wreaked havoc with mixtures and I could be driving along the freeway at a steady speed when it would all of a sudden smooth out, gain power and add about 15mph with the same throttle setting.
Then, a minute or so later it would go back into suck-mode and be it's usual crappy self.
That's when it even ran of course.

When it wouldn't start at all, it turned out to be the Ford-specific relay for powering the ECM. Under the hood next to the battery it took a beating from corrosion. Even replacing it did not do the trick, so I cut the connector off, changed over to a standard Bosch type relay and everything was hunky-dory after that.

Still had no power, but at least it ran.

Paul

 

[Viperwolf1]

Sounds like the old EEC3 system. EEC1 and 2 only lasted about a year each. EEC3 was used on carbed and CFI motors until multiport EEC4 came out.

 

[Steve83]

I don't think I've ever run into an electronic carb on a V8 Ford truck, but I fought a few 300ci feedback carbs. I can't remember if they have MAPs, though...



Yep - it's there on the R side of the engine (lower L of the vacuum map if you zoom in):



This might be a voltage MAP:

 

[DirtDonk]

Interesting. Firefox is reporting your images as being on "Reported Attack Pages!" and asking if I want to know more, or my favorite, the "Get me outta here!" button.

Paul

 

[jw0747]

answer to original question...yes, you can mount it under the dash.

 

[kholding]

Thanks again everyone. I may actually be more confused than when I started this thread but as long as I know I have the right BP sensor and under the dash works, I'm good!

 

[OX1]

Yes. EVERY one that I've tested was voltage-varying. I've never bothered hooking up a frequency-varying MAP to a tachometer or scope or anything else to test it because they're so common in JYs & cheap at parts stores that I just swap a known-good one every time. I probably have 6 common MAPs in my junkpile, and a few more in my tool box - I collect them at JYs when I'm buying big parts, so they don't charge me for the little stuff like that.

What's the oldest Ford EFI you've worked on? I think mine was an early-80s (maybe 82) LTD or Mark with TBI.

84 LTD TBI V-6 was the oldest I've messed with. Over the years I've tested MAPs with a vac pump and frequency capable meter and never seen one that does not match that chart.

That includes

84 LTD V-6 TBI
86 Capri 5.0
86 LTD V-6 TBI
86 Mk VII LSC
89 MK VII LSC
89 Bronco 5.0
89 Mustang 5.0
91 Mustang 5.0
93 Ranger 5.0 MA (converted from 92 stang)
93 Merc GM
95 F250 460

 

[Steve83]

Paul
Yeah, there's something going on with SMN's certificates that Chrome & FF don't like. I'm sure it'll get straightened out soon...

 

[Viperwolf1]

Paul
Yeah, there's something going on with SMN's certificates that Chrome & FF don't like. I'm sure it'll get straightened out soon...

It's not just that. My symantec on IE is saying it has java malware.

 

[Steve83]

Interesting... I run Avast, SpyBot, & IoBits MWF, and none of them detect any problems. My system is set up according to this guide:
http://forums.majorgeeks.com/showthread.php?t=44525

 

[chuzie]

So just to completely clear, are we saying that and EEC-IV MAP sensor (87-93) has identical output as a BP sensor and the only difference between the two is a single exterior physical characteristic pertaining to the presence of a nipple.

If I need a sensor for my A9L or A9P or A3M, I can just run to the junkyard and pull a MAP sensor and use it as a replacement BP?

It is tough finding a BP in the junkyard these days. There are plenty of MAP sensors though.

 

[Hank_]

Thanks again everyone. I may actually be more confused than when I started this thread but as long as I know I have the right BP sensor and under the dash works, I'm good!

Ken the sensor you show is the same one I have in my bronco with EFI. The only difference is I took the guard off the nipple and mounted a tassel.;D

Henry

 

[chuzie]

Thanks Hank.

However, I am looking for more empirical data linking the frequencies / tables between the two sensors.

Only the following have been tested by OX1:

84 LTD V-6 TBI
86 Capri 5.0
86 LTD V-6 TBI
86 Mk VII LSC
89 MK VII LSC
89 Bronco 5.0
89 Mustang 5.0
91 Mustang 5.0
93 Ranger 5.0 MA (converted from 92 stang)
93 Merc GM
95 F250 460

I would like to get confirmation all the EEC-IV MAPs are the same as the BPs. Otherwise, I have to assume that the select few that have pulled MAPs and used them as BPs have possibly gotten lucky or do not necessarily notice a difference, if any, between the two.

 

[chuzie]

Not sure where RJM got their data but looking at the charts on their site, it looks like using a MAP sensor in place of a BP will cause the EEC to think it is at a much higher altitude and lean the fuel delivery.

Reference:

MAP: http://oldfuelinjection.com/index.php?p=27

and

BP: http://oldfuelinjection.com/?p=32

Thoughts?

BTW- Don't compare their graphs, they are identical. Look at the data below.

 

[Steve83]

No, they're identical. The first chart (his p.27) is absolute pressure (positive), but the 2nd is vacuum (negative) adjusted to a local 30inHG BP. That's why they have the same graph, but different outputs. Ryan got his info from the PCED:

...
This Pinpoint Test is intended to diagnose only the following:
- MAP/BP sensor (9F479)
- Harness circuits: VREF, MAP/BP SIG, and SIG RTN
- Processor assembly (12A650)
- MAP vacuum line

Description
The Manifold Absolute Pressure (MAP) sensor operates as a piezoelectric (pressure-sensing) disc. However, rather than generating a voltage, its output is a frequency change. The sensor changes frequency relative to intake manifold vacuum. The sensor frequency increases as vacuum increases. The MAP sensor allows the EEC processor to determine what the engine load is. Its signal affects air/fuel ratio, ignition timing, EGR flow and altitude compensation.

The BP sensor is used to sense the changes in barometric pressure, allowing the EEC processor to sense the altitude at which the vehicle is operating. Its signal affects air/fuel ratio, spark and EGR for altitude compensation.
...
NOTE:
MAP sensor output frequency versus manifold vacuum data is based on 30.0 in-Hg barometric pressure.
...

 

[chuzie]

Gotcha. Well, that explains why, when I plotted the data in Excel, the data points were inverse. I just missed the labeling of the RJM chart that said "Vacuum." Whoops!

Thanks for clearing that up for me.