more crappy running FI questions

[Brant]

Hi everyone...
I need Ideas or advice. Car is still running poorly, and somebody up there obviously wants me to learn more about D-Jet..

specifics:
1972 1.7 motor installed into a 74 chassis
DJet car, very stock and a bit worn.. smokes a bit (not fresh)
Motor ran fine in different chassis, and then sat for 1.5 years before being installed into this car. I thought I had accounted for all of the wiring harness changes between years, but I'm open to suggestions at this point.

The problem:
at higher rpm the car pulls very slowly and barely accelerates. I discovered by accident that if the car is cold and has set for 3+ hours it runs strongly for about 1 mile, and will pull up to redline then...

Then once warmed up it feels down on power. In 2nd gear it will pull to redline, but takes forever to accelerate past 5000rpm. In 3rd gear it would take one mile to pull to redline and becomes noticeably down on power above 4500rpm. Throw a mild hill into the mix and it will barely hold its own speed, or even looses speed. 4th or 5th gear are just worse.

Also, sometimes there is a small amount of bucking between 3000 - 3500 rpm. (When engine is warm)

Also, I hear tiny backfiring when air cleaner removed and at higher rpm

What I've done:
-set valves multiple times
-pulled injectors and they had a nice spray cone pattern to them when cold.
-set timing multiple times (advance works good, and holds vacuum) Advance is fairly steady and idle is steady.
-new plugs, plug wires
-new fuel filter
-disassembled, clean, lubricated, and reassembled distributor with new points, condensor, dwell set, and vacuum pot works. Rotor and cap have 5000 miles on them and look good still. FI points look good.
-Fuel pressure checked and set to 29.6lbs
-MPS holds vacuum when tested by mouth for 1minute (may not mean much the way I tested it)

I feel like I've nearly eliminated the ignition and it must be a FI control at this point. I initially thought it was an advance issue, but that seems to be working well. When I changed the plugs #4 looked very rich,and I assumed that plug wire might have been bad or something.. Now I keep checking it and it looks brand new, so I'm wondering if its not getting gas or something. Could injectors quit working when warm, or could fuel pressure be dropping when warm?

I'm starting to think that the car is getting rich or lean when it warms up. I say this because I'm trying to figure out what would change and I know the cold start can increase or decrease the amount ouf fuel put in.

Could an AAR closing cause system to go rich?

I'm not sure what to check next or how to check it.
thanks again, and I appologize that this is the 1000th time people have heard about a crappy running car.
brant

[Dave at Pelican Parts]

You've seen Brad Anders' website, yes? Read through it thoroughly?

Sounds like you might have crud in your fuel tank. It can block the inlet to the fuel supply system and drop the amount delivered. Conversely, you might have a bad CHT sensor. Read through Brad's site (http://members.rennlist.com/pbanders) and start checking stuff.

--DD

[pbanders]

OK, to start with, the AAR not closing will not cause the system to go rich..... so you don't have to worry about that.

First, I suggest looking at my web pages for diagnostic information. It's very hard to diagnose problems when I'm not certain if the owner has gone through a systematic analysis of their running problems. That said, here are a couple of comments.

Have you checked the compression and your idle vacuum level? You say the motor is old and smokes - maybe its got low compression, sticking valve, etc. Next, if you're sure this is an FI problem, you need to determine if this is a lean or rich condition problem. Generally, when a motor is very weak in performance, I'd suspect a lean condition. T4 motors love to run rich. Here, I'd check the head temp sensor at cold and hot, using values from my web page for normal responses.

[Brant]

thank you sirs.. I'll read further.. I've looked but didn't know where to begin. I'll definitely check the head temp though..

I was thinking lean also, due to changing the spark plugs and then showing no discoloration at all..

compression could be better: 115/115/105/90
but it ran good before and now won't accelerate on the most modest of hills or onramps.

definitely something wrong.

Fuel tank was removed... cleaned twice, and put together with new filter. Internal filter is I think removed (ex-race car)... All fuel lines on motor are new, all vacuum lines on motor are new. Fuel lines in center tunnel were replaced a few years ago with steel brake lines... fuel pressure good upon test.. Would a fuel pump loose pressure when warm?


If it was a head temp sensor... would this normally cause a rich or lean failure mode.. ?

brant

[pbanders]

Your compression looks ok. Have you put a vac gauge on the intake manifold to see if you've got any dynamic problems? You should get something near 15 in Hg of vacuum at idle, steady.

CHT's can fail lean or rich, but generally, fail rich (open circuit).

[Brant]

I haven't put a vacuum guage on it.. I know it has a strong vacuum to my hand.. but I will borrow a guage and try that...

thanks again everyone.
brant

[Brant]

Brad,

I hope you catch this.. as I have another question or two.

I pulled the cylinder head temp sensor and got a few measurements. They vary with your webpage recommendations, but then you state that they can vary from sensor to sensor....

I'm assuming that my numbers indicate a bad sensor (ie: I may have found my problem?) what do you think? my nubers were:

#280 130 012
3000 @38 degrees F
1150 @ room temp of 65 degrees F
190 @ boiling water (5000 ft elevation)

I also took a measurement in the car hot and cold.. however I grounded the meter onto the battery ground and not the block if that matters (maybe I screwed up)... anyways cold was around
70degrees F and was 1300. And warm was with engine oil temp in the low operating range (don't know the actual temp) and was 150 on the meter.

what does that sound like to you?

My ECU is 022 906 021E (0 280 000 037)

I didn't yet remove the MPS to find the number but I know it is the same one that ran well on the car 2 years ago.. I'll be buying a vacuum guage this week...

in the mean time I think I'll order the CHT sensor and hope that fixes it....

thanks everyone.
brant

[Brant]

bump...

how about it.. do my readings fall within the normal manufacturing variences or does 150-hot sound like enough to screw up the high rpm running and cause a loss of power?

guess I'll try a new one and see if there is a difference?

b

[Dave at Pelican Parts]

150 ohms hot should be fine. That's below the threshold where the CHT has no effect. The 70F reading might be a tiny bit high, but that will only have an effect for a few minutes at most.

Look through Brad's web pages. There's a ton and a half of D-jet info there, just about everything that is known about the system any more!

BTW, the sensors just love to strip the threads out of the hole in the head. I wouldn't change it unless I knew it was bad, or unless I knew it had been changed in the past handful of years. (A "fresh" install is less likely to strip than a 30-year-old one.)

--DD

[pbanders]

As DD says, your boiling water reading is spot-on, and your "hot" reading looks ok. However, your 70 deg. F reading of 1300 ohms is too low, and will cause the car to be quite lean during warm-up, normal readings are much closer to 2K ohms. Your 38 deg. F reading is low, too. I'd replace the sensor.

[Brant]

shoot... I was hoping that I had found the problem...

what is the thresh hold that matters... for the low range?


On Brad's page is says that an 012 style sensor should read 2.5K @68 degrees F... so I thought for sure I was outside of the range when cold since mine reads 1150 cold.... but its when my motor is warm that it runs like crap... so I didn't know if my warm reading was within or outside of the range...

I've already got it removed (luckily with no problems) which is how I did the ice water and boiling tests.

thanks
brant

[Dave at Pelican Parts]

Hmm, looks like I was wrong on the warm/cold readings. (See Brad's note; got in just before yours.) He knows much more than I do about the D-jet; he has studied it much more intensely than I.

Mostly this is so you realize that Brad replied.

--DD

[Brant]

Thanks Dave I do truly appreciate all of your help....

Dang.. looks like I'll have to keep searching for it.
Hmm... back to the drawling board.
(I will replace the sensor too, just to be sure..)

Anybody got a set of carbs they want to sell??? just kidding

brant

[pbanders]

Brant, the low readings during warm-up on your CHT sensor would not explain the poor running conditions you describe in your first posting in this thread.

I really don't like doing diagnostics like this over the web, as I'm never sure of what the owner has actually done or what condition the car is in. You need to make 100% certain that your car is mechanically right (compression and vacuum), battery/charging system is in perfect operating condition (good supply voltage when running), ignition is perfect (all components correct, in good or new condition, timing and dwell and gap all to spec), and that fuel supply and fuel pressure is to spec. Once you're 100% sure of ALL of that stuff, AND you've checked your vacuum hoses to make certain they're in top condition and plumbed correctly, THEN it's time to look at the FI system. There really aren't that many components to the system. If it's not obvious in initial testing as to what's wrong, I strongly recommend renting the VW1218 tester from Pelican. This tester will evaluate every single component in the FI system, including the FI trigger points in the dizzy, which are often neglected and in poor condition. The alternative to the tester is to swap in known good components and see if your problem goes away. In terms of frequency of problems with FI components, here's my list:

1. MPS (often wrong p/n, rebuilt and poorly calibrated, leaky, etc.)
2. TPS (worn out, causing jerky operation at steady throttle)
3. FI Trigger Points (worn out, causing missing, jerky operation, etc.)
4. Injectors (clogged, wrong p/n, leaky)
5. The rest of the stuff in the system....

Also, don't forget the wiring harness. Many problems are due to cracked and/or corroded connnections. Big problem is the ground junction at the back of the engine, easy to have a corroded or loose connection here that goes unnoticed.

[Brant]

thats fair sir...
so I'll call pelican and try to figure out how to rent the tester.
(anybody tried this before?)

I have gone through compression (when cold but not hot.. yet), new plug wires, new fuel filter, set valves and timing thrice, new plugs, new condensor, rebuilt or at least disassembed cleaned and reassembled the distributor, dwell, timing, fuel pressure, all vacuum hoses replaced and routed per pelican diagram, (NOT MPS, which is the correct one or at least worked well in combo before), pulled fuel tank, opened fuel pump and reassembled...

-I have not recalibrated the TPS but sysmptoms don't lead me to expect that.
-I have not yet purchased a vacuum guage to test MPS (I borrowed one to test vacuum diaphram on distributor)
-I pulled injectors and observed them for pattern when cold, but not hot and not professionally tested.
- I unplugged and looked for corrossion and reconnected all of the wiring harness ends, but probably need to give more attention to this.
- I'm wondering if changing from an early to a late chassis would have caused me to miss something in the relay board and its connections which would influence the system?


Basically I have more to do.. but I did read your web page and have tried a lot of things... just trying to figure out where to go next.
brant

[Alfred1]

Originally posted by pbanders
I strongly recommend renting the VW1218 tester from Pelican. This tester will evaluate every single component in the FI system, including the FI trigger points in the dizzy, which are often neglected and in poor condition.

Woo hoo! I've got one of those and I even bought a 75 page manual for it today. I didn't even know until last week that there was a manual for it.

[Alfred1]

Originally posted by Brant
so I'll call pelican and try to figure out how to rent the tester.
(anybody tried this before?)

Brant, here is some info on renting the tester from Pelican and the instructions .