Feeling rich? One for the FI guys! Options

[Rod]

Hi all, it’s a FI diagnosis I’m after, please help.

1973 1.7L standard FI system.

When hot after a long run, I have a really rubbish tick-over and car wants to stall.

I thought it would be MPS as mine has already been opened by a PO, but it reads 94 ohms on the outer coils and 398ohms on the inner terminals. It seems to hold vacuum too (only tried sucking on it, don’t have a gauge) so can I rule that out??

I really want some further checks to do as it’s running so rich I can see smoke at a hot idle and it’s difficult getting it to pull away without bogging down (only when hot - it’s great when cold!!) So it’s a hot only problem I’m having.

Thanks for any help.

[JeffBowlsby]

Hi Rod,

It could be a number of things. Did this behavior just begin or was there a preceding event like...just changed the injectors-TPS-TS2-ignition timing, fuel pressure, etc. Have you treid to adjust the ECU idle mixtrue knpob on the ECU to correct the condition?

A mouth such test is no where near good enough for an MPS vacuum test. Get a handled vacuum pump with a gauge, and pump it up to 15-18 inHG.

If rich, the first things I would check are:

Full mechanical review - ignition timing, valves, compression test
Unplug the FI harness from the CSV
Disengage the CSV
Failed/failing MPS
Failed/failing TS2 (cyl 3 sensor)
Too high fuel pressure
Leaky fuel injectors or cold start valve - get them cleaned/flow tested

[Rod]

Hi Jeff,

Thanks for your reply. Can you put that MPS aside I emailed about earlier for me (if you have one in stock after checking)

No nothing has recently changed. A few months back went through everything and all seemed to be okay. Fitted electronic Ignition and all that is working well too. Just the last couple of times after being out for a long run it comes home limping and rich..

The mixture screw when turned anti clockwise upped the idle a little last night with a click or two - didn’t want to go twisting it any more.

[Rod]

Ah! One thing I did notice tonight was that the MAP sensor was
Loose in its mounting.. it only has one rubber mount and it was very loose so was able to rattle about on recent journeys.

Would this have damaged it internally?

[rjames]

Did you adjust the MPs for the proper AF ratios? If not, you need to.

[Rod]

Did you adjust the MPs for the proper AF ratios? If not, you need to.

I have never had the MPS apart myself, it has screws on it rather than rivets though, so has been opened before obviously.

I have no idea what settings it’s at.

[Rand]

Did you adjust the MPs for the proper AF ratios? If not, you need to.

I have never had the MPS apart myself, it has screws on it rather than rivets though, so has been opened before obviously.

I have no idea what settings it’s at.

Go home. Substitute a known good MPS, try again. Report back.

[76-914]

Sounds like the CHT has a bad connection or is failing. Do you have an adjustable rheostat/variable resistor that you can plug inline to evaluate? Also, check your return line to be sure it isn't pinched/blocked. The latter will give you very poor gas milage. Ask me how I know this. (IMG:style_emoticons/default/headbang.gif)

[dr914@autoatlanta.com]

if you cannot figure it out, you can call me and I will work you through it. If the car was running fine until you added the pertronix, that unit could have failed too, other than that, like previously stated:
head temp sensor
fuel pressure
manifold pressure sensor
leaking vacuum line going to the manifold pressure sensor
sticking cold start valve (rare)

other things:
bad valve adjust causing low compression
pertronix disfunctioning
bad gas

[Rand]

George, it's cool that you offer personal help. But this is a forum where thousands are here to help. We don't need to be sending people away from here to you. You can still help here.

[rgalla9146]

George, it's cool that you offer personal help. But this is a forum where thousands are here to help. We don't need to be sending people away from here to you. You can still help here.

I agree
The OP is knowledgeable and capable.
Every one of these dialogues builds a larger base of enthusiasm and
skill.
Allow this process to run its course.
This is not a vending opportunity.

[Rod]

Did you adjust the MPs for the proper AF ratios? If not, you need to.

I have never had the MPS apart myself, it has screws on it rather than rivets though, so has been opened before obviously.

I have no idea what settings it’s at.

Go home. Substitute a known good MPS, try again. Report back.

Ok, good shout. I hadn’t realised before last night that my MPS had previously been taken apart and rebuilt for some reason, the symptoms do point to this failing, So what with it being apart and me not knowing what’s been done internally I think it’s a good idea to change it. Jeff has one that he’ll rebuild this w/e so I’ll probably get that in to cross that off the list.

Sounds like the CHT has a bad connection or is failing. Do you have an adjustable rheostat/variable resistor that you can plug inline to evaluate? Also, check your return line to be sure it isn't pinched/blocked. The latter will give you very poor gas milage. Ask me how I know this. (IMG:style_emoticons/default/headbang.gif)

No, I don’t have a variable resistor or the patience to find one, fit it and investigate. For the money they are new from Porsche, I’ll get one and change it in any case. Have ordered this tonight...

Which return line? And where are the kink points??

George, it's cool that you offer personal help. But this is a forum where thousands are here to help. We don't need to be sending people away from here to you. You can still help here.

I agree
The OP is knowledgeable and capable.
Every one of these dialogues builds a larger base of enthusiasm and
skill.
Allow this process to run its course.
This is not a vending opportunity.

I appreciate both George’s post and yours.. I enjoy the diagnosis of such problems, so hopefully we’ll get there, plenty of George’s parts here already.

What’s the best way to check fuel pressure? You guys refer to a harbour freight kit, but I’m in the UK.. been looking but can’t find a >30 gauge.

[Rand]

I'm just saying George should contribute here. He wants everyone to come to him. Not cool. Let us keep it here for everyone.

[Rand]

Checking fuel pressure means putting a gauge in line. It's really simple. Others will tell you the best place to insert it.

[rjames]

The MPS you get from Jeff will still most likely need to be adjusted to get the correct AFR for your engine. I just went through this myself. Tangerine Racing sells the MPS adjustment tools, but you will need an O2 sensor to know where your at. Plex makes a grood/affordable one that connects to your phone via Bluetooth if you don’t want to install a gauge.

[Jonathan Livesay]

I'm just saying George should contribute here. He wants everyone to come to him. Not cool. Let us keep it here for everyone.

Well he is trying to run a business. What smart businessman trying to sell anything doesn't.

[Rod]

The MPS you get from Jeff will still most likely need to be adjusted to get the correct AFR for your engine. I just went through this myself. Tangerine Racing sells the MPS adjustment tools, but you will need an O2 sensor to know where your at. Plex makes a grood/affordable one that connects to your phone via Bluetooth if you don’t want to install a gauge.

My car is a factory standard 1.7 and I want this one to remain this way. Do I really need to set the MPS to this specific car? Are there not factory 1.7 settings that Jeff knows about? If they were sealed and set at the factory and teh car is standard I don't understand why the extra adjustment might be necessary.....?

[JeffBowlsby]

The MPS you get from Jeff will still most likely need to be adjusted to get the correct AFR for your engine. I just went through this myself. Tangerine Racing sells the MPS adjustment tools, but you will need an O2 sensor to know where your at. Plex makes a grood/affordable one that connects to your phone via Bluetooth if you don’t want to install a gauge.

My car is a factory standard 1.7 and I want this one to remain this way. Do I really need to set the MPS to this specific car? Are there not factory 1.7 settings that Jeff knows about? If they were sealed and set at the factory and teh car is standard I don't understand why the extra adjustment might be necessary.....?

Hopefully things will be plug N play, but...The unknown is not the MPS values, its the condition and needs of the rest of the engine and its injection system. Sometimes, when a new component is installed, it becomes evident that other adjustments to the engine or its FI system have been made to compensate for some condition that needs further adjustment to work well with the new component. Each engine is different, and if adjustments are needed (they are not needed every time) you may be able to make simple adjustments if necessary such as to fuel pressure, the air bleed screw, or the idle mixture ECU knob, injector flow rates (clean them or replace leaky ones!) or the ignition system, etc. This explanation may clarify:

"MPS calibration notes: Rebuilt MPS are calibrated to the known values of NOS MPS’s. These values are verified to be generally accurate for the specified engines, but may not be precisely correct for your engine, because your engine may not be in the same state of tune, wear or condition as a factory new reference engine used to determine the NOS MPS calibration values. Consider that the MPS calibration provided is as close as possible, but for optimum performance your engine/fuel injection system should be evaluated on a dyno or exhaust gas analyzer and adjusted accordingly by a qualified technician. So that the MPS can be accessed easily for adjustment, the outer MPS stop receives only a drop of clear nail polish to hold it in place and not a full epoxy seal."

[Rod]

Ok I understand. Let’s get the parts in and then see what happens.

Have ordered a CHT sender and a few elbows from Porsche, I will redo the Rickover and mixture when all installed. My local garage can hook it into their static co2 machine to do the ECU mixture, the part load readings are a bit trickier - no rolling road.

[Rand]

I'm just saying George should contribute here. He wants everyone to come to him. Not cool. Let us keep it here for everyone.

Well he is trying to run a business. What smart businessman trying to sell anything doesn't.

It's fine to participate to gain business exposure, not to try and extract people away from here. Very different. What ethical business man does that? Enough on this, sorry I brought it up.