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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Old 11-04-2012
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Volvo MD7A Not Starting

I had my injectors rebuilt on my md7a. Put them back in and it ran good but the idle speed was little high. Adjusted the idle down to about 800 and it idled fine. Turned it off and tried to crank again then it sputtered a few seconds and it will not start now. Have replace all filters and bled it forever. Have tried startng with vaious ammounts of throttle and it acts like it wants to hit but end up just getting white smoke. Took the injetcors out and had them tested and they are fine. Thinking it may be the high pressure pump at this point. There are no bleed screws on whatever high pressure pump this is. Maybe the white smoke means it is getting fuel but not at proper time or ammount. Anyone have any ideas or does it sound like it is high pressure pump rebuild time?
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Old 11-05-2012
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Re: Volvo MD7A Not Starting

Did this problem exist before you had your injectors serviced? Given that the engine wouldn't start after you made adjustments to the pump, I assume you have tried reversing those adjustments? Is there unburned fuel coming out the exhaust, ie a slick on the water? Which injector pump have you got, the CAV or the Bosch?
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Old 11-05-2012
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Re: Volvo MD7A Not Starting

Start with the easy stuff, it sounds like the engine is no getting fuel.

Are you sure that the shutdown is really in the correct position, I have found this to be the cause a suprising number of times.

Are you sure that you are getting solid fuel at the injectors and no air? You really need to bleed all of the air out which can be time consuming and frustrating. Any air in the injector line will prevent the injector from popping off which means that you will never purge the air and you will be in a never-ending cranking cycle. If you ran your injection pump dry, they hold a large volume of fuel and can take quite a while to refill (one of my engines holds over 1 gallon in the IP, don't worry, your volvo holds significantly less) If you have any questions as to whether you bled properly, I would suggest that you post exactly what you did so that people can give you feedback. Also, since you have replaced the filter and broken other connections, you should really make sure that you haven't created an air leak, especially on the suction side.

Beyond that, answering SchockT's questions would be helpful.
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Re: Volvo MD7A Not Starting

I have checked for leaks and there are none. After I had the injectors rebuilt the motor started right up. It was idleing at 1100 so I adjusted the screw that keeps the throttle where it is back until I got it to 800 and it ideled fine. I cut it off and tried to restart and it just sputtered a few secs and cut off and would not restart. I pulled the injectors and had them tested and they are fine. If you break loose and injector line at injector connection, there is fuel coming out on both. If you hold your hand over intake it sucks your hand in so it is getting air. I put the idle screw back to where it had been before and it will not start. I replaced filters and checked all my lines and bled it according to the manual 5 times over 5 days and it still will not start. Had some people who know deisels and they are scratching there heads. No blown or leaking head gasket either. If you try and give it a little throttle while cranking it will start to put out white smoke like it is getting fuel but it never runs. I may try and replace the spin on filter that mounts on the engine"even though I just did this for troubleshooting" just to make sure I did not get a bad one and bleed again but since the injectors are good and it is getting air and no blown head gasket and if you give it some throttle while cranking the smoke turns white the only other thing anyone can think of is that the 30 year old high pressure pump is not putting out enough pressure to make the injectors pop correctly.
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Re: Volvo MD7A Not Starting

Do you have access to high and low pressure gauges? Knowing fuel pressure at the inlet and outlet of the IP really helps with diagnosing something like this. It is usually pretty easy to hook up one on the inlet side but the high pressure side tends to be trickier and is more dangerous so you need to make sure everything is rated for the pressure.

When they serviced the injectors, did they make note of what the pop off pressure was and did they raise it? Over time, the pop off pressure tends to trend down and that may have masked a different problem.
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Re: Volvo MD7A Not Starting

I have not been able to find anyone with the pressure tester you are talking about. I have thought about the same thing to make completely sure it is the high pressure pump especially since a rebuild of it will be around $500.
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Old 11-06-2012
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Re: Volvo MD7A Not Starting

It is pretty easy to make your own gauge for the low pressure side, you just need to work out the different fittings. You can also buy one, many mechanics have them. A high pressure gauge is much harder and requires finding things that are rated to the pressure.

Good luck.
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Old 11-06-2012
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Re: Volvo MD7A Not Starting

Sounds like a compression check might be in order, just to be sure ( is there a decompress. lever? is it set properly?).... and I hope you have the RWC intake shut while you're cranking.....
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Re: Volvo MD7A Not Starting

So the last thing you did before it started acting up is shut the engine down. I assume you shut down by pulling the fuel shut off. You might want to check the linkage and cable on the engine kill knob, and make sure it hasn't slipped, stretched or broken. Failing that, perhaps you are right, and the pump needs an overhaul. Perhaps it cannot generate the pressure required by the freshly serviced injectors, however it is strange that it ran the first time you tried it. If you haven't got the tools to test the pump,and your compression, it might be worth while to pay a mechanic to come down and spend a couple of hours on it.
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Re: Volvo MD7A Not Starting

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Originally Posted by itsme1414 View Post
I had my injectors rebuilt on my md7a. Put them back in and it ran good but the idle speed was little high. Adjusted the idle down to about 800 and it idled fine. Turned it off and tried to crank again then it sputtered a few seconds and it will not start now. Have replace all filters and bled it forever. Have tried startng with vaious ammounts of throttle and it acts like it wants to hit but end up just getting white smoke. Took the injetcors out and had them tested and they are fine. Thinking it may be the high pressure pump at this point. There are no bleed screws on whatever high pressure pump this is. Maybe the white smoke means it is getting fuel but not at proper time or ammount. Anyone have any ideas or does it sound like it is high pressure pump rebuild time?
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