Volvo Penta 7.4GI Crank - No Start - No Injector Spray

[PartsChaser]

Hey guys - working on a new to me 98 Crownline 266BR with the VP 7.4 MPI Engine that will crank, but not start on its own -- without a sniff of starting fluid/brake cleaner. I can get it to start/idle/run with fluid, but never on its own. When running this way, it still pops and hesitates like its got injection issues.

To date I've verified pressure at the low pressure and high pressure pumps (within range per the Seloc manual) and I have good spark.

Question:

With the intake plenum off - I see no fuel from the injectors during prime, or start/crank. I should see at least something I'd assume, unless 1) they are totally clogged (all 8) or 2) some signal to the ECM is being blocked like a bad sensor, etc.

The boat does not have any type of warning buzzer/beeper going off - and the fuel filter was just changed by me to rule that out, along with the low pressure pump. Fuel pumps kick on and run as they should.

Any thoughts on ECM or sensors that may be shut off during the cranking process? Any ideas why it would start and run with starting fluid but not lite on its own?

Thanks in advance!

 

[Fun Times]

For chasing parts it will help to know your full engine model or serial number.

The ignition start cranking system for injecting fuel, creating spark timing, and a host of other things needed to get the engine up and running starts within the distributor assembly which is called the pick up coil mounted to the distributor shaft assembly....From there is the ignition module that should be mounted under the distributor cap too if it's the system I think it is.

Since the engine runs; it helps tell you the coil is okay at this point but there's a chance the Module isn't working properly internally possibly not switching over from crank to run mode or vice versa.

One quick theory test could be you could try lightly tapping on the ignition module to see if it seems to help any with starting. From a boat dealer this module is pricey but you'd be able to find one at an auto parts store for less which would work the same.

Should (or may) look like these,
http://www.iboats.com/Boat-Parts-Acc...&q=3854003
https://www.ebay.com/itm/Genuine-Vol...-/371790258350

Your issue could be a host of other issues too but the module sounds suspected to at the very least start off with in your testing's...Also while the following test guide is for a GM truck, etc., the concept would be the same. http://easyautodiagnostics.com/gm/4....ed-icm-tests-1

 

[PartsChaser]

Thanks Fun Times - that's where I was heading next.

For reference - I believe my engine is the 74GIPBYCCE

Last night I did some digging/testing and found that the injector rail has 12V with the key ON, but when cranking it drops to around 9V (Battery drops to roughly 10.9 during cranking). New Batteries/fresh charges.

Also - I checked each injector to ensure it would actually spray with 12v manually applied via test jumper wires - all 8 fired ok, so I think the injectors are good. Something in the signal between the ignition module/ecm and the injectors seems to be in play, so I'll replace that IGN Module and re-test.

 

[Chigwalla]

...but when cranking it drops to around 9V...

9V is typically the bottom end of normal while cranking: that spec should be in your manual somewhere.

Don't be TOO quick to blame the module - they're rarely the problem.
A physical blockage inside the rail or lines will manifest those symptoms.
You can have pressure but not flow - that's a typical failure mode for a pump. Get back into the manual and look for a "fuel pump output test" that involves measuring the fuel pumped over a specified time interval.

"... pops and hesitates like its got injection issues."

'Pop' suggests timing rather than fuel delivery.

 

[Dave-R]

Does that year of engine have a crank sensor? If the ECM does not have that reference the fuel injection system will not operate. Make absolutely sure you have a fully charged battery. You might be ahead to have a dealer read the ECM for codes. Electronic issues are hell to find without the right equipment. Dave-R

 

[Scott Danforth]

also, clean the battery cables. the electronics shut off at 9 volts

 

[PartsChaser]

Sad to say, I am throwing in the towel on the MEFI fuel injection system. I've backprobed all the ECM connections, confirmed the power and grounds are good, etc.. still no luck. I had a local boat shop lend me 2 different ECM's (neither were exact matches so I knew it was a longshot) and no dice there either.

Going to convert it to a 4BBL with HEI and know that I can make it run, old school.

Thanks again for all the inputs gents. Too much hassle, time, and expense for me at this stage of the game.

 

[Fun Times]

Have you tried using a noid light at the/each injector harness to see if you're getting the light to flash? That would help give you some indication if it's a bad signal or fuel flow issues..... https://www.harborfreight.com/11-pie...set-97959.html

Just so you're aware, You won't see any fuel flow through the injectors during first initial key-up where the fuel system is self priming....The fuel spray will only happen during crank or running modes....when everything is working normal of course.

Another test you could try would be with your fuel pressure gauge connected to the high side, build your fuel pressure up with cycling the key on and off a few times, Next disconnect the fuel pump wiring connector, Then crank the engine over and see if the fuel psi goes down and how much.

 

[PartsChaser]

Have you tried using a noid light at the/each injector harness to see if you're getting the light to flash? That would help give you some indication if it's a bad signal or fuel flow issues..... https://www.harborfreight.com/11-pie...set-97959.html

Just so you're aware, You won't see any fuel flow through the injectors during first initial key-up where the fuel system is self priming....The fuel spray will only happen during crank or running modes....when everything is working normal of course.

Another test you could try would be with your fuel pressure gauge connected to the high side, build your fuel pressure up with cycling the key on and off a few times, Next disconnect the fuel pump wiring connector, Then crank the engine over and see if the fuel psi goes down and how much.

Sadly, yes - the noid would blink, but not as bright as I'd seen before.

Also tried with building up fuel pressure/starting with a cracked throttle, etc. Still no luck no matter what. I re-did the grounds, provided direct power to the ECM via a different path, etc. No fuel spray when hooked to the ECM. I've removed the injector rail and provided 12v to them manually, and they spray and you can hear them click, so I am decently sure I dont have 8 injectors bad - especially since I can get it to start with a whiff of starting fluid. Not ideal, but part of the troubleshooting.

 

[Fun Times]

I can't post the link here as the link will be dead but search online (Re: 1998 7.4 MPI No Start, Good spark, no fuel dun dun dun....) and read post #5.

Since you may be seeing lower voltage type issues, One other thing that could be wrong is there is a diode, resistor, capacitor type device inline of the pink wire that runs between the coil and distributor module that could be bad not allowing the system to work correctly....An ohms check sometimes finds the issue and sometimes not.

It is item number 40 Volvo part number 3854084, http://www.volvopentastore.com/Ignit...view_id.772473

Try bypassing that device and see if it helps...It's under the tubing and I believe some tape or heat shrink....Image search the part number online if needed....Good luck.