SumDarkPlace Posted January 16, 2017 Share Posted January 16, 2017 I'm sure this has been discussed a few times in the past, and I've been searching the forum but to no avail. I have a RRC 3.5 flapper (4CU ECU) in my 90. It's not run right since I got it a couple of months ago. The main issue is cold start: it fires briefly then dies, next try does the same, and so on, each time getting slightly warmer, and running slightly longer, until it starts and ticks over normally. I've set the TPS to .325, disconnecting the 9th inj makes no difference, all wires and plugs checked. What's my next step? Coolant temp sensor? air flow meter? Any advice appreciated, I'm new to the rv8, and have just bought a 2nd one! (2001 Thor P38 4.0) Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 16, 2017 Share Posted January 16, 2017 In the tech archive, look for the flapper efi diagnostics, that will get you through a process that should narrow things down. I would suspect the CTS though, can be tested with a multimeter with the figures in the tech archive Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 17, 2017 Author Share Posted January 17, 2017 I tried the tech archive. The link to the .pdf was broken. Does anyone have a working link? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 17, 2017 Share Posted January 17, 2017 I have reported the broken links, and pointed them at the attached file maint_fuel_injection.pdf Fingers crossed that will work for you Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 18, 2017 Author Share Posted January 18, 2017 Thanks, that link works I'll run through some tests this morning, and hopefully have a handle on what's wrong. Later this year I'm going to replace the system with MS, so I don't want to spend much money on the current system. Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 18, 2017 Author Share Posted January 18, 2017 CTS is duff, reading 170 Ohms at all temps. Ordered a new one. Would this also result in the engine dying when the throttle is pressed quickly? It revs normally if the pedal is pressed slowly, but dies for a quick press. TPS is set correct, but I haven't checked air flow meter yet. Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 18, 2017 Author Share Posted January 18, 2017 I decided to recheck the TPS following the test process in the linked .pdf above. Voltage set right, and increases smoothly to 4.3V, but the injectors are not clicking as suggested by the instructions. However, as the engine isn't running, the injectors shouldn't fire, I think? When the TPS increases voltage, should the ECU be increasing the duty on the injectors? My symptoms would suggest that this isn't happening, and the slow pedal press acceleration is solely due to the airflow meter reading increasing duty. I tried disconnecting the airflow meter while running, and the revs increased slightly, but the throttle behaviour was the same. I think I may have an ECU problem Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 18, 2017 Share Posted January 18, 2017 Given your CTS is telling your ECU it is -40C, I would bargain that once that is sorted everything else will be OK given it is at least running -it definitely will cause bogging on acceleration for one. The other issue I'm unsure of, but then I am much more familiar with the hotwire set up. Do you hold the flap open in the test you describe? Either way, wait on the CTS, reckon all else will be OK Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 18, 2017 Author Share Posted January 18, 2017 Reading 170 Ohms is 100C, so pretty much normal operating temperature, so it should run right once warm. With the flapper, even when disconnected the flap will move, it just won't be sending a signal to the ecu. Running with the AFM disconnected means the ecu should only have a signal from the TPS to vary the injector duty for acceleration. What I don't know is what the ECU does when it doesn't have an AFM signal. When I disconnect it ticks over at slightly higher revs, and a slow movement of the throttle increases the revs initially, but a fast press kills it. This pretty much the same as with the AFM connected. I would expect that the ECU would respond to a TPS signal with immediate increase in fuelling to cover the lag before the AFM tells it how much extra air is being sucked in. Then the ECU should compare the two signals to adjust the fuel to match the load. Basically the TPS tells the ECU to accelerate, the AFM tells it how much load to accelerate against. I'm guessing this is compared to revs as well, which will also change the duty based on the map characteristics. I've got a spare ECU borrowed from a friend. Is the later PRC7440 ECU interchangeable with the earlier PRC4764 unit? Both are 4cu lucas units, but I don't want to blow up my friend's ECU unnecessarily! This thread has become something of a dump for my stream of consciousness on this problem, sorry! Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 18, 2017 Author Share Posted January 18, 2017 I also tried disconnecting the TPS with the AFM connected, the symptoms described didn't change at all. It made no difference. Quote Link to comment Share on other sites More sharing options...
smallfry Posted January 19, 2017 Share Posted January 19, 2017 Just a hunch, but try swapping the ignition module............ Quote Link to comment Share on other sites More sharing options...
SumDarkPlace Posted January 20, 2017 Author Share Posted January 20, 2017 CTS has made a lot of difference, it starts from cold now The hesitation is still there. I finally got a timing light on it too, and discovered that the distributor will not rotate far enough to get it to 10 BTDC. The vacuum unit is jamming tight against the water pump. Currently set to 8 BTDC, which sounds like it's running nicer. It was set 0 BTDC before. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 20, 2017 Share Posted January 20, 2017 8 should be very good if on petrol. To get more turnage, then you will have take the distributor out and rotate it, and then move the leads round one notch. Sounds like you don't need to though. You checked the TPS? Smooth and non-glitchy? Quote Link to comment Share on other sites More sharing options...
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