740 starting issues

Pez

Hi everyone,

A year ago i picked up this Volvo which had likely overheated and was only just holding on as i purchased it. Since then I've had the head reskimmed and installed a new head gasket, leads, spark plugs and repaired the fuel relay.

Recently i've started with an usual problem of which i'm either not describing / searching for correctly or i just can't the correct information, i'm hoping the information and video's im going to attach to this post will signal something i can work on.

The Problem:

My car *Sometimes* struggles to turn on, it cranks and starts to idle "HORRIBLEY", although the rev's seem to indicate that its sitting around 1k. See a video of this below, (There is an exhaust leak currently it's kind of small makes it a bit harder to hear).

startup-slow-1.mp4

1MB

Here is a second video where its a bit more auditable as to what's going on, to me it sounds like the engine is building momentum, until it's got over this starting hiccup the car can't move under its own power. Although once completed it can. You can see the rev meter go from just under 1k to build up to something around 1250 and until its good again and settle at just around 900~ish.

startup-slow-2.mp4

14MB

This issue occurs either with a hot or cold start, but seems to happen more often after sitting for a few days, typically the startup is very quick to the point where im wondering if its unhealthy see below: (too much of a good thing? 🙂 )

quick-start-1.mp4

864kB

quick-start-2.mp4

1MB

The car is a B230F LH 2.4, the on board diagnostics reads 1-1-1 for both the testing areas ( forget which each pin is for but there are seemingly no errors), 3 or so months ago I ran a compression test on all 4 cylinders and they where healthy all within 10% of each other around 160-170.

The end goal for this car is to replace my other car as my daily driver and use it solely, i know this might be risky but i travel a short distance for work and to the shops etc and any other longer travel we typically do in my partners car. Although this can't happen without resolving this lingering issue. I'm not super technically minded but i'm trying to do everything myself as i don't have access to people local to me in WA to assist or a shop to take the car to.

I have a longer 6 minute video i can upload (if its even possible to post here) that shows the car with its shitty start, getting to a normal idling spot then driving flawlessly after, if you'd like to see it if you think it helps let me know. The only other issue with the car in my opinion is the lack of up hill power / acceleration (foot to the floor and what i consider to be slow shifting) Although i'm also aware that this just might be a volvo thing and my unrealistic expectations.

Thanks

Pez 🙂

Todds940

Hey mate, I had some idling and starting struggles on the 940 (not quite as bad as you) and spending some more time on electricals got it under control. Cleaning fuse/relay pins (and holders), taking apart relays to repair solder joints, checking grounds etc. FWIW I had replaced the fuel pump relay prior to doing this and it changed nothing.

(100% not an expert here!)

Pez

Todds940

Thanks man will do, i think i should touch up the radio suppression relay as I believe that affects the fuel injectors, i've done it once before on another car, but when i checked this one it didn't appear to be too bad but maybe some fresh contacts for each area will help, what spots did you do in particular

ramrod

Maybe flawlessly is a bit of a stretch, but it runs well. I've never been up to 100 km p/h as it's not gone on the freeway yet as to be honest i havn't been the most confident with this car yet.

I've purchased a timing belt light previously and that was spot on where it should be i believe its like negative 10*? I can't remember off the top of my head but i did manage to get a video of it when i did it i might have to check.

I would say the engine is sluggish to respond underload, i've only fixed the fuel relay on this cars fuel system, after resoldering you could hear it click and the pump prime on key turn. There aren't other symptoms really, it could use some new bushes i believe as sometimes the car jolts swapping between drive & reverse, and the AC doesn't work 🙂 But none of these would really affect the current issue i have i believe.

jamesinc

Cold compression just meaning not having the car up to temp? If so that is what i did the first time around and yielded those results. haha,

Would leaking injectors just be a new rubber and filter kit? Or a brand new set of injectors?

I'll have to try out the multimeter i hadn't checked it previously, i think i have a spare too.

Thanks everyone will get onto testing some of these areas over the next few days or so.

ramrod

So you say once the engine starts and runs for a while, it then runs flawlessly?

Is it just hard to start, idles roughly til it warms up then settles down to a smooth 750rpm balanced feeling idle?

How does it perform under load? What has been done to the fuel system? How responsive is the engine? What other symptoms are there? How old is the ignition system? Is the cam timing correct? A lot of different parts not being at 100% can cause what you’re experiencing.

Does it get up to 100 km/h and seem like it has power in reserve to overtake?

jamesinc

My first thought would be a fuel issue, like leaking injectors, or a leaking cold start injector. If the engine tries to start but there is excess fuel, it runs like shit (or just cranks) until the fuel is cleared out.

Also given the engine's history, a cold compression test would be a good sanity check.

It's possible also you have a bad O2 sensor and your computer has the fuel trimmed badly, you can test O2 sensor operation really easily with a multimeter, looking for a constant sweep in the 0V-1V range on the fat green wire, you should find a connector inside a rubber boot somewhere around the brake booster.

ramrod

Not talking about ignition timing here, which on your model is not adjustable.

Camshaft timing. The relationship between the camshaft and crankshaft.

When some people remove the belt or the cylinder head, they can easily make the mistake of putting the belt on one tooth out. Very common.

Check the timing marks are correct and move on from there

Pez

ramrod I'll need to check, that can just be rotated clockwise by hand to return to original position? Might not be able to do that until this weekend though, not alot of spare time this week

ramrod

You need to turn the crank to get the mark on the pulley to meet with the zero pointer on the timing cover. Then check the cam pulley mark meets with the mark on the plastic cover behind it

If it’s 180° away, further turn the crank another 180° so the cam then meets up with the mark.

Pez

ramrod Can do, will post results when i can 🙂

jamesinc

Leaky seals you would see, they'd leak fuel out onto the manifold, you'd see and smell it. It would be the injector, either it could be clogged , or it could have spray pattern issues (you can get pintle cap kits).

You can pull the rail off the manifold, put the injectors into cups, and crank the car to check flow and pattern (make sure to connect the ground wires for testing).

ramrod

You can temporarily disable the suspect injector and notice if the idle changes at the same time.

This might be a more complicated problem though than a simple misfire, seems to be heat related and intermittent.

The rule is, verify correct engine mechanical health and timing accuracy, and the bibles always make mention of checking the obvious health parameters like compression and valve clearance checks, as well as vacuum leaks before condemning any of the control systems such as fuel and ignition