problem starting think it is fuel pressure.

hoodsy · Post by **hoodsy** » Sun Jul 23, 2006 10:11 pm

well after years I finally got to the point of trying to stat my 412. it is freshly rebuilt with new injectors and ignition parts and fuel lines. it is a D-jet it cranks over, but does not start. I have spark and the injectors are functioning on both throttle and trigger points. my fuel pump is working, but when I checked the fuel pressure when the pump come on it spikes up to pressure but immediately the pressure drops off and there are no leaks. there is a part in the fuel line that my manual refers to as a muffler, it is the disc shaped part in the line after the pump. my main question is.. is this really supposed to be a check valve, I have worked on alot on fuel injection systems and usually you should have residual fuel pressure and years ago when the car was running I seem to remember it have residual pressure in the line. if this part is supposed to be a check valve than I knoe for sure it does not work, I checked it already to see if it would check. if it is a check valve can I replace it with a aftermarket check valve? anyway as it stands after cranking the engine the plugs are dry and the engine barely makes a cough. any help, ideas or info would be greatly appreciated. I am so close and yet still so far,

raygreenwood · Post by **raygreenwood** » Mon Jul 24, 2006 6:36 am

The "muffler" as the book calls it...is hollow. It is really just a harmonic pulse damper. It is designed to cause the fuel to lose the pulses that come from a combination of the pump rotor and the opening and closing of the injectors. It does this by causing the fuel to abruptly change direction in two planes. Its subtle but it does work. It will never stop you from starting with or without it in line.

If you fire up the fuel pump....and then shut off the engine and you have no leaks....and the pressure does not stay within a range of 18-23 psi for at least 30 minutes....you most probably have a bad fuel pressure regulator. To get a definitive test of the regulator....pinch teh return line off PARTIALLY.....not all the way. What you want to see...is if you can artifically make teh regulator work by restricting it downstream. If it still drops quickly...then the problem may be the spring check valve in the pump. That is actually not common. The fuel pressure regulator is generally bad whenever the system has sat for any extended length of time. This Also....check the resistance (ohms) head temperature sensor. If it is off....or if the single wire connection is not pristine...it can cause a no start with fuel and spark present. Ray

vwbill · Post by **vwbill** » Mon Jul 24, 2006 6:28 pm

Have you pulled the "8mm"screw out of the left fuel injetion rail at the test tee? You could put a hose on it there and put it in a jar and see what the pump output is before the pressure regulator?? Have you checked the tank sock and fuel filter? bill

hoodsy · Post by **hoodsy** » Tue Jul 25, 2006 9:45 pm

thank you very much for the great feedback. I am going to borrow a better fuel pressure tester from work and try and see if I can resolve the problem. I do know that the pump is pumping fuel no problem and the sock filter appears okay. but the pressure in the line drops very rapidly once the pump has stopped. I will have more acurate analysis this weekend when I can great back over to my shop with some proper test equipment.By the way, ray, you said the head temp sensor could cause a no start even with fuel and spark? is that because it stops the pump from pumping during cranking? similar to how most systems rely on the oil pressure sensor to control the fuel pump?if so I should be able to eliminate that issue by jumping the pump selenoid, correct?

raygreenwood · Post by **raygreenwood** » Wed Jul 26, 2006 2:01 pm

If the fuel pressure drops very rapidly once the engien is turned off...you most likely have a bad regulator. If it has not run for some time....and even if it has....it is common for water vapor in teh fuel to rust and pit the little plate that causes pressure on teh line. It leaks. It is also vaguely possible that the relief valve in teh pump is stuck of rusted. If pinching the return line about 3/4 closed on the regulator...causes pressure to drop off slower...then it is the regulator. Ray

hoodsy · Post by **hoodsy** » Sun Jul 30, 2006 9:14 pm

well I ran some tests and sure enough the regulator was nfg. so I put in a spare I had. Now I have a different problem. when I crank the engine over the injectors do not fire. the trigger points are activating the fuel pump, so I know the triggers are working. the injectors fire when I move the throttle, so I knoe the injectors work. in fact at one point while I was checking them they did in fact fire while cranking but now they don't. I tried swapping different mps units.. no change, checked the head temp sensor, and it has no resistance, although i tried cranking with it unplugged no change. tried a couple of different seat belt interlock relays, no change. I tried a couple of ecm's no change. I am getting fuel pressure, the injectors will inject when throttled, the trigger points are working as they are sending a signal to the fuel pump, I maintain 28 psi fuel pressure no problem, the ingition works fine. only two injectors fire at a time when throttled and no injectors are firiing when cranking, although at one point during earlier testing they where. the car started and ran extremely reliably before being parked for several years for restoration. the engine is rebuilt the vaccume hoses are new, injectors are new. etc. but still no go, so if you guys have any ideas for what I should do next or can draw any ideas of what the problem is from what I have explained please all input is greatly appreciated .

raygreenwood · Post by **raygreenwood** » Mon Jul 31, 2006 7:45 am

Stooooop! DO NOT SWAP components!!! This is the surest way to get totally lost. It is 100% wrong. Simply disconnecting and reconnecting a plug on a component may be what actually cures or changes the problem.....and now you may never know what is actually wrong.

The MPS by the way has absolutely nothing to do with wether the injectors inject or not. It is the load sensor that helps to determine how long they stay open.

The trigger points do nothing to the fuel pump. The fuel pump runs when you turn the key for about two seconds. Thats a function of the ECU.
If the injectors are not firing...you either have bad or loose grounds under the plenum at the case centerline....there is a bunble of 3 pairs of ground wires under teh plenum. They must be tight and clean.
The triggers are generally dirty or the rubbing blocks worn....or the resistance too high on the trigger point connections.

Remove the triggers...clean them with fast evaporating contact cleaner. Remove all teh grease. Then...drag a slip of paper...from a brown paper bag between each contact set.....several times....use nothing harsher than this. Do not bend or adjust the triggers. Put high temp grease on teh cam in teh distributor. With your voltage/ohmeter...test each trigger circuit. That would be first with the left terminal and center then the right terminal and center.
Ideally...the resistance should be within about .1 ohms of each other...and neither side should be over about 1.1 ohms. An accceptable reading would be say..... .8 ohms for one side and .9 ohms for the other. The lower the better. It could be as much as say..... .8 and .7ohms. If one side is working but not the other...you will get no injection. Ray

hoodsy · Post by **hoodsy** » Mon Jul 31, 2006 10:52 pm

okay I did what you suggested with the triggers. and they tested fine, I cleaned as suggested anyway. let me clearify things alittle. I know that when you turn the key that the fuel pump comes on for a few seconds, I know that this is not affected by the triggers. now that being said, on my car, if you turn on the key, and use a remote button tocrank the engine, the fuel pump comes on and off with the triggers. if I don't crank the engine but leave the key on and rotate the distributor to open and close the triggers the fuel pump turns on and off with the triggers, if you unplug the plug from the triggers and jump the terminals to mimic the opening and closing of the triggers the fuel pump comes on and offf. so yes the fuel pump is being activated by the trigger points this is how it can mintain fuel pressure with the injectors opening and closing. now at no time are the injectors firing with the trigger points, which they should. if one set of triggers are activated 1 and 4 will fire on the throttle, when the opposite triggers are activated the throttle will fire 2 and 3. moving the throttle fires the injectors no problem. now I am wondering could the possion of the throttle sensor be causing a no fuel condition, and if so if I adjust it slightly would it possibly rectify the problem. once again all ideas are welcome. dave

raygreenwood · Post by **raygreenwood** » Tue Aug 01, 2006 9:24 am

Dang......I ahve actually seen this before. Memory failing. The timer for the fuel pump is activated by a single white wire from the ECU to the starter. Check all of your connections at the starter. Also...and I know its tediuos....but check all 23 wires from the ECU (yes you will need to pull the plug)....but check each wire from teh ECU....they are numbered....and make sure it is going to the correct place...and make sure its resistance is not high.

Its possible something may be out of whack with the TPS. I can't remember if it can cause this. Make sure it is closing all of the way. You will have to remove teh TB with teh TPS to properly adjust it. Whene you pop off the black plastic cap and close the TPS with your fingers on teh throttle plate....tell me what you see inside...and tell me what part number is on teh back of the TPS. Ray

Bobnotch · Post by **Bobnotch** » Thu Aug 03, 2006 8:30 pm

Also, you might want to pull the injectors out and have them spray into a cup or something just to verify that they're doing their job. I'm only mentioning this, because I ran into this while trouble shooting my own car (t-3 with a t-4 in it) and running the t-4 D-jet FI system. On mine the fuel pressure kept dropping slowly after attempting to start. It had a leaking #1 injector. I replaced that one, then the pressure held steady, but still wouldn't start. I decided to check the spray pattern on the rest (using a t-3 dizzy to trigger the injectors). Turns out the other 3 weren't spraying at all.

I replaced them, and the engine fired right up. Note, this was after I checked the valve gaps again, and making certain the ignition timimg was spot on.

I hope this helps.

hoodsy · Post by **hoodsy** » Sat Aug 05, 2006 10:36 pm

well good news I finally got the ol gal fired up. I checked every component in the system, and all checked out perfect and was about to throw in the towel when I decided to take one last look and lo and behold two of the wires to the mps had broken at a joint in the harness. so a quick soldering jod later a bang, she fired right up instantly. now I have one further question. I have installed an mps from a type three as my original one was hooped, so can anyone, ray, tell me how to adjust it to run on a type 4. I probably have any test equipment that may be required. I know you usually have to adjust the mps slightly to run on a type 4 so if anyone knows how please let me know.

raygreenwood · Post by **raygreenwood** » Mon Aug 07, 2006 5:55 am

Yow! It takes a bit of driving and experimenting. I have written much on this. You might do a search.
Also....soldering anywhere in the EFI harness is a no-no. It flat out will cause problems, The best thing to do in teh case of a broken off connector...is to clip all of the connectors off at the affected plug and crimp on new terminals. In the case of a mid-harness break...use crimp on telecom connectors and again clip all associated wires at the same joint with that component.
When you get it up and running....its worth it to invest in a new harness. Ray

hoodsy · Post by **hoodsy** » Mon Aug 07, 2006 10:54 am

well I did solder the the mid harness break and it works great. I cannot believe that a properly done job with quality solder and sealed with heat shrink is not better than crimp connectors. crimp connectors cause more resistance due to oxidation that occurs in them etc. I work in the marine industry on engines and electronic systems and believe me a sealed consistant joint is better than connectors any day. as long as it is done right I believe it is just fine. besides the mps is adjustable, so any bit of added resistance can be compensated for. any way the car starts up perfectly, and that is the main thing wether we agree on the methods or not. thanks for your ideas and input it has been appreciated. I will check out your write ups on the mps.

vwbill · Post by **vwbill** » Mon Aug 07, 2006 2:33 pm

She runs!! Great news!! That was a good catch and could have been a pain to find! Any driving yet or outta the question yet?? I just want to hear another driver out there! How is your motor? I can't seem to get the rebuild right at the heads and think I might have to go to professional help! Can't keep hitting my head again that wall..... Good luck with the setup and I found the valves are key and the timing set at the high rpm as per specs is key!! Pressure is as Ray always tells us is key too!

Thanks for posting the progress!! bill

raygreenwood · Post by **raygreenwood** » Mon Aug 07, 2006 3:40 pm

Solder is actually MUCH MUCh MUCH MUCH ....worse..... than proper factory crimp connections. The fact that it is impossible to keep solder joints free of micro-voids....with any equality.....and the fact that using flux based solder promotes corrosion....and the fact that solder is more brittle than teh metals in modern crimp connectors ....and the fact that vibration and heat cycling over time will exploit all of these weaknesses....is why there is not a single modern aircraft, or automotive wiring system that is still soldered in any of its joints outside of a relay enclosure. I would suspect that there are few marine electronic applications that use them either...because all of factory crimp connectors and weatherhead seal are Mil-spec....and solder joints are not.

Crimp type connectors are vastly superior. They have almost no corrosion problems due to the many types of plating and the seals employed. With adjustable die compression settings and very uniform construction of the connectors....they crimp extremely uniformly.

The company that makes about 90% of all EFI connectors world wide (not to mention for every single commercial aircraft company)....AMP....has done TONS AND tons AND tons of testing and research on crimp connectors. Do some research into the available papers (1000's) on the AMP website that is on Tyco industries website.
Much of it.....was done in the wake of the utter failure of the terminals our D-jet uses. It is what lead to the development of the dual cantilever spring terminal connector....which is in nearly universal use....with some 15,000 variations. It is also why...the terminal types in D-jet....were never again used for fuel injection anywhere.

The only company to NOT use AMP connectors is GM. This is also why their injection is miserable. They have dozens of re-calls compared to very few on Japanese and European fuel injected vehicles. They have good componets....but their systems are seldom reliable over 70-90k miles. They start picking up "un-duplicatable faults".

Also....the MPS...cannot adjust for variations in resistance. It has no control over that.
Yes...if some variations in resistance are simply affecting just your overall fuel mixture......across the entire range....then of course you "could" adjust ......somehwat.....at the MPS. A less problematic method would be to tweek the fuel pressure. Then your load sensing is undisturbed.
Examples of malfunctions that cause an across the board shift...would be poor quality grounds.....or voltage drop....none of which are the fault of load sensing....though you "could" adjust for them at the MPS.

That....by the way.....would be an incorrect method of compensation. The MPS...is a load response device....not a fuel mixture adjuster.
If you end up having to adjust for an electrical resistance problem .....by tweaking the screws and changing the spring pressures in the MPS........yes.....you may fix an initial fuel mixture problem.....but you also altered the MPS response to both vacuum load and climatic changes. It creates problems all over the place. The correct response when finding resistance that is incorrect......is to correct that wire or connector.

That is one of the main problems with D-jet that people do not understand. D-jet....works....100% on resistance. The resistance settings within teh ECU....are locked. The harness should be locked as well. No changes allowed.

In most D-jet problems....the integrity of the wiring harness is usually part of the problem. Its actually pretty easy to build a new one. There are only 23 wires. I changed all of my terminals to L-jet terminals. Much much better connectivity and reliability. It makes the system clean enough that you actually will usually need to reset your fuel mixture when you are done putting in a cleaner harness. Glad you got it running. Lovely cars! Ray